Which IMD do you mean? The first Google page has about a dozen alternatives.

And what sort of problems -not opening, not rendering properly, links not working . . .?

Have you tried another browser for the site? Are you having problems with any other site?

If you do have Fx 3.06 you are open to serious security problems. You should update to Fx3.6.17 if not not Fx4.

imd its internet downlod maniger-sory my english is not god- it was ok when i use fairfox 3,6 when i use fairfox 4 the last the imd dos not worke so i go bak to the old 3m6 thanks

http://www.internetdownloadmanager.com/

You probably need to update IDM.
Internet Download Manager v6.05 build 14. Fixed compatibility problems with different browsers including Internet Explorer 9 Final, Mozilla Firefox 4 ...