Mail & Safari Will Not Open/work

tea please

Hi, so, a bit of background:
I'm running an iMac G5 with OSX Panther, had it for less than a year.
My hard drive completely crashed about a month ago, had to get it replaced, lost everything. Since the fix, on and off I was having problems staying connected to the internet ( thought at first that it was just my service provider, but I'm not so sure.)

3 days ago I turned on my computer to find that I can not access any applications that require an internet connection ( mail, safari, internet explorer, limewire...)

I called my local mac store, and theyy reccommended I do a re-install. I ran a hardware test, came out clean. I re-installed OS-X , and for about 2 hours everything was working, but now I only have access to the internet through Internet Explorer.

When I try to open Mail it shows up on the dock, but that's it. when i control click it says application not responding, and all I can do is force quit. same with all the other internet related applications ( except for IE, weird, but I'm thankful )

with this and my previous data loss ( i run a design business from home) I'm about ready to tear my hair out, do you have any suggestions?

Thanks in advance!