From what I've gathered, both Avast and Zone Alarm create browser problems. I strongly recommend AVG Free. In my opinion, it's the best and most of all it's FREE. Now, my guess is that your browser's been hijacked or corrupted, so here's some nfo 4 u 2 follow. C if it helps u any:
The following six tips can help restore your browser's settings:
1. Stop cascading pop-up windows.
If a seemingly endless number of pop-up windows appear on your screen, you'll probably want to stop the deluge first. To do this in Microsoft Windows Vista, Windows XP, or Windows 2000 while using Internet Explorer:
Press CTRL+ALT+DEL, click Task Manager, and then click the Processes tab.
Click IEXPLORE.EXE, and then click the End Process button.
This closes all instances of Internet Explorer. Then you can re-open the program to continue browsing as usual. To help prevent future attacks, you should also have a pop-up blocker turned on. To turn on the pop-up blocker in Internet Explorer 7:
Click Tools menu, click Internet Options, and then click the Privacy tab.
In the Pop-up Blocker box, select the Block pop-ups check box. Click OK.
If you still experience the other effects of a hijacked Web browser, try the following:
2. Install preventive software such as the kinds mentioned in the preceding Preventing browser hijacks section. Many browser hijacking programs can be identified and removed by downloading, installing, and running these programs.
3. Run the malicious software removal tool. This can catch some, but not all, kinds of hijacking software.
4. Reset Internet Explorer settings. If you're using Internet Explorer and your home page has been changed, you can often reset it yourself.
Close any Internet Explorer or Windows Explorer windows that are currently open.
Open Internet Explorer.
Click Tools, and then click Internet Options.
Click the Advanced tab, and then click Reset.
In the Reset Internet Explorer Settings dialog box, click Reset.
When Internet Explorer finishes restoring the settings, click Close, and then click OK.
Close Internet Explorer.
Your changes will take effect the next time you open Internet Explorer.
5. Disable add-ons. Many browser hijackings come from add-ons, also known as ActiveX controls, browser extensions, browser helper objects, or toolbars. These items can improve your experience on a Web site by providing multimedia or interactive content, such as animations. However, some add-ons can cause your computer to stop responding or display content that you don't want, such as pop-up ads.
To learn how to disable add-ons in Windows Vista or Windows XP Service Pack 2 (SP2), read How do browser add-ons affect my computer?
6. Removing unwanted programs with the Add/Remove feature
If you're ready to try some advanced removal methods, the Microsoft Help and Support article Unexplained computer behavior may be caused by deceptive software provides additional steps you can take, including how to use the Add/Remove feature, the built-in program remover, and the program finder in Windows Explorer.
7. Empty the Recycle Bin when you've finished these steps, especially if you've removed an unwanted program. Then restart your computer.