internet apps crashing

Hi - the obvious questions first...
- have you checked the event viewer, (you're running Windows, right?)?
- have you updated the anti-virus and anti-spyware programmes lately?
- do you have a firewall running?
- is your Windows installation fully patched and updated?

Making sure everything is current is probably the place to start, and when you mention internet applications, are these a browser and e-mail client, or something else?

You often need multiple spyware scans by dift pgms to find
you don't mention which you are running.
http://www.trendmicro.com/spyware-scan/free_spyware_scan.asp
has a free online scan.
the webroot 30 day trial is good and finds some others don't.

other less likely causes could be basic system instability from lack of normal maint: scandisk, regclean, defrag.. or even memory or hardware failure (fan stopped, overheating for example) or dust in case.