The subject behavior will occur if you left Norton CleanSweep installed when you upgraded.
To work around the problem:
1. Press CTRL+ALT+DELETE and then Task Manager.
2. On the File menu, press New Task (Run..).
3. Type control and press Enter.
4. Select Add/Remove Programs and remove CleanSweep.
If this doesn't work for you, try the following:
1. Press CTRL+ALT+DELETE and Shutdown / Restart your computer.
2. Press F8 to enter Safe-mode.
3. Select the Safe Mode with Command Prompt.
4. Change to the %SystemRoot%\System32 folder.
5. Rename Apitrap.dll Apitrap.old
6. Restart the computer.