As much as I want to have fun with this thread, I will be good this time. More information such as, I just upgraded to Windows 7 or I spilled water on my keyboard, etc.. would be helpful to judge what your problem may be.
My guess is you have a keyboard and mouse that's not compatible with Windows 7. I had that same problem so my spidey senses are telling me that's your issue.
Give more detail and I may be able to give a better answer...
ha ha u scared him away on that note i have something similar i have Defender matador 550 in other words peace of crap when i type something in chat or web url the cursor jumps back to the beginning its quiet bothersome. I have win 7 64 tested it on my friends pc too same crap so its the win7 x keyboard problem probably and i cant seem to find any drivers for defender keyboards if u have some knowledge im ready to hear it out