Download the full, offline Service Pack 3 installer from the link below.. Once that's done, after cleaning all the Temporary Files from the computer, defragging, then temporarily disabling your antivirus program, run the file to reinstall SP3. It replaces and repairs any glitchy files or settings and should help.
http://www.microsoft.com/downloads/details.aspx?FamilyId=5B33B5A8-5E76-401F-BE08-1E1555D4F3D4&displaylang=en
Hope this helps.
Grif
All of a sudden, every time I boot, the desktop icons and background come up normally, and the mouse icon moves - but NOTHING on the desktop that I click on works. The mouse arrow becomes a hourglass icon on the blue bar at the bottom. No new software or hardware.
The ONLY way to recover is to go to safe mode and restore to an earlier time. Interestingly, even if the restore says it was NOT successful to an earlier time and unchanged, the machine then works normally (until the next reboot). I've done: sfc scannow, crapcleaner, utility drive and registry scans, antivirus scans, chkdsk, etc - no help. I've looked carefully at ipconfig, but only the bare bones usual stuff is there. I'd be grateful for any suggestions. Thank you.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic