Just to add on.
If it was not behaving the way you have mentioned in the past, it is most likely that:
1. your com caught a virus/malware
2. some sites are just overloading your browser with huge images and stuff
3. some part of your hard disk was corrupted, and it happened to be on IE's program files (rare)
4. one of your com hardware went nutz (v rare)
You can:
1. Try using another browser like
Opera and see if a similar situation occurs.
2. Scan your com with AVG or Kaspersky for viruses and malwares.
3. ChkDsk or memtest86 to check your hard disk and RAM respectively.
4. Start working and save up $ for a new com instead.