Frontpg.exe error:Default/Homepage files

FrontPage 2000,IIS4,NT4 System:
Got hit by the Nimda virus a few weeks ago. Downloaded the fix and everything was running well. Now I’m having trouble with FrontPage errors. Can’t open a default.htm or homepage file on the web site with FrontPage 2000. Get Frontpg.exe error and the FP program closes. All other files open OK. Strangely, I’m able to open the default and home page files from my home PC and edit them! I use a cable modem from home.