AVG has announced that they have discontinued support for version 7.5 of they software at the end of February. This means that if you're using it, you will no longer get updates.
You will need to update your antivirus. If you have AVG 7.5, you probably have already seen a warning screen.
First of all, don't be fooled; the "warning screen" may, upon closer inspection, be an Antivirus 360 warning. You don't want to mess with that. AVG has the AVG logo on it -- a square with four different colored sections. Anything else is suspicious.
Another sign that this is legitimate is that when you close the window, it stays closed. In any case, your best solution is to go directly to the AVG download page at http://free.grisoft.com and find the free version. Current version number is 8.5. AVG will suggest you get the paid version, of course, but the free version is easy to find.
Important! There are reports of problems on Vista machines with AVG 8.0 running Firefox. If you use Firefox, do not install the AVG linkscanner or toolbar when installing AVG. If the problem still recurs, uninstall AVG and switch to Avast Antivirus.