After SP3, need to press CTRL-V twice to paste, other problems

After upgrading to SP3 (version 5.1 build 2600.xpsp.080413-2111: Service Pack 3), when I copy something to the clipboard and go to paste it with CTRL-V, I must press that twice. I can paste using the right-click Paste with no problem. But, must always press CTRL-V twice to paste after the update. Wish I could figure out why and correct this. Build "2600??" :-D

Also, after upgrating to SP3, whenever I press a button on a website using IE, like Login, Go, Submit New Thread, Send, the browser doesn't respond for about 5 to 10 seconds. Then, it processes the request. I've been running the same version of the browser (7.0.5730.11) for over a month and this only started happening after the upgrade.

In addition, sometimes I will get an error with a hexidecimal number after a browser crashes for no reason. Sometimes, when I press a button within the browser. This is particularly painful after typing up a response to a thread in a forum, submitting it and then it crashes, resulting in me having to remember to copy the contents before submitting. Once, the machine totally froze - I had a great cursor on the screen, but nothing would work.

All these problems have been going on for about 2 weeks since I did the upgrade. Any ideas what I can do to try to fix it or is it time to start all over again with a reinstall up to SP2? I rebuilt the machine about 2 years ago and it's been perfect until now. Thanks!