Application problems that occur on Windows XP Service Pack 2 (SP2) fall into two categories: software that isn't compatible with SP2 and software that doesn't function properly until you modify the firewall to enable necessary client-to-server and server-to-client communication. If you’re testing SP2 or you've already upgraded and see unexpected behavior or error messages from antivirus software, third-party firewall software, games, and utilities, you might need a vendor-supplied update. The Microsoft article "Programs that are known to experience a loss of functionality when they run on a Windows XP Service Pack 2-based computer" (http://support.microsoft.com/?kbid=884130) has a lengthy list of programs that aren't compatible with SP2. Either the applications don’t install or function properly, or they interfere with normal XP operations. Although not all-inclusive, the list provides a starting point for troubleshooting incompatibilities.

If the misbehaving utility or application doesn't appear on the incompatible list, it might fall into the second category and you need to modify XP’s firewall to enable communication. This is especially true of client-server style applications because default firewall settings can block packets that are sent from the server to the client. If the firewall blocks server communication, the client likely will hang or fail with an error message. I discussed known firewall problems with some commonly deployed enterprise packages, including network backup software, in "Application Problems in XP SP2" (http://www.windowsitpro.com/article/articleid/43798/43798.html).

Since August, Microsoft has created a more comprehensive list of applications that require firewall modifications. You can see this updated list in the Microsoft article " Some programs seem to stop working after you install Windows XP Service Pack 2" (http://support.microsoft.com/?kbid=842242). The article contains step-by-step instructions on how to modify XP’s firewall to enable network backups and other applications. It also documents some of the ports you need to open to enable various programs. In some cases, the article identifies the port or ports you need to open, but in others (e.g., for Microsoft Systems Management Server—SMS), the article refers you to the product documentation.

Cleaning Up after MS04-024
When you search for a directory or file that's mapped to a remote share on Windows 2003, Windows Explorer might incorrectly report that the file or directory doesn't exist by presenting the status message “Search is complete. There are no results to display.” This bug, a side-effect of Microsoft’s MS04-024 security hotfix, can occur on SP1 systems on which MS04-024 has been installed and on all SP2 systems because SP2 includes this security hotfix. To eliminate the bug, you need to patch and reboot Windows 2003 and XP. See the Microsoft article " No results are returned when you search for files or for folders over a slow network link in Windows Server 2003 or in Windows XP" (http://support.microsoft.com/?kbid=885843) for details.

Windows Installer
IBM’s Rescue and Recovery with Rapid Restore application uses a filter driver that operates at a very low level to monitor system activity. When you run Windows Installer, a bug in how the installer accesses files collides with the filter driver (and potentially filter drivers in similar applications), causing XP SP2 systems to hang. You’ll see this exact behavior when you attempt to install any of 16 hotfixes listed in article "Computer stops responding when you try to install an update in Windows XP Service Pack 2" (http://support.microsoft.com/?kbid=885894). Before you put any of these hotfixes on systems with a filter driver, download and install the Windows Installer bug fix. Available at the download center, the bug fix has the generic name of “Update for Windows XP Service Pack 2 (KB885894)" and a release date of October 10.

Smart Card Bugs
On the subject of smart cards, XP SP1 and SP2 systems might hang and require a reboot to restore operation if you remove a smart card after you log off. The Microsoft article " Removing a smart card immediately after you log off a Windows XP-based computer may cause the computer to stop responding" (http://support.microsoft.com/?kbid=883529) indicates that Microsoft Product Support Services (PSS) has a bug fix for this problem on SP1 and SP2 systems. To update SP2 images, you need winlogon.exe, version 5.1.2600.2508, with a file release date of August 26. The SP1 bug fix for this problem updates two files, licdll.dll and winlogon.exe; both files have a release date of August 26, but the winlogon.exe fix for SP1 has an earlier version number.

A different Winlogon bug can interfere with network connectivity when you log on with a username and password on an SP2 system that has a smart card attached. The Microsoft article "The network provider may not function as expected on your Windows XP-based computer" (http://support.microsoft.com/?kbid=885423) doesn't document specific symptoms that occur as a result of this bug. Microsoft has a hotfix for this problem on SP1 and SP2 systems. The version of Winlogon that corrects this problem, which has a file release date of September 29, is the most current for both service packs. I recommend you ask for this hotfix, rather than the previous one.

AOL Disconnect and Download Failures
A bug in how XP handles Network Address Translation (NAT) connections can randomly disconnect you from AOL and incorrectly abort AOL downloads midstream. These two problems are caused by XP SP2, not AOL. To restore AOL functionality, call Microsoft PSS and ask for the new version of ipnathlp.dll, which has a file release date of September 1. Cite the Microsoft article "AOL file downloads may abruptly stop or AOL broadband connections may be dropped after you install Windows XP Service Pack 2" (http://support.microsoft.com/?kbid=885295) as a reference.

RTF Print Bug
A bug in how XP processes Rich Text Format (RTF) print files might show only the first page in a print preview and might print only the first page when you send the output to a printer. The Microsoft article "Only the first page of a Rich Text Format (RTF) document may preview or print in an application that uses Msftedit.dll on a Windows XP-based computer" (http://support.microsoft.com/?kbid=883483) indicates that Microsoft PSS has a new version of the faulty component msftedit.dll, with a file release date of September 30, that correctly previews and prints RTF files.