The subject behavior is indicative of a corrupted registry key.

To resolve this problem:

1. Copy / Paste the following to a FixSearch.reg file:

REGEDIT4

\[-HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\User Agent\]

2. Merge the FixSearch.reg file with your registry, or run regedit /s FixSearch.reg.

3. Shutdown and restart your computer.