Monthly Archives: May 2008

Fix for Firefox received a message with incorrect Message Authentication Code

Recently when browsing with Firefox, I kept getting a popup message box: …received a message with incorrect Message Authentication Code. This happened every time I visited GMail, or any other ssl site via htttps://. I searched everywhere for a solution to fix this annoyance, and finally found my solution in the MozillaZine forum at this link: http://tinyurl.com/5wnhs7

The fix to this problem is to enable a firewall on the user’s PC.

This is the fix that worked for me. During my search for a fix I noticed that this is a widespread problem with Firefox.

It seems that this message occurs in Firefox when one disables the Windows firewall service. I had inadvertently disabled the service, and that was when the messages started occurring. After I enabled the Windows firewall service the “incorrect Message Authentication Code” messages stopped.

According to the people at the MozillaZine forums, any firewall will do, it is not necessary to use only the Windows firewall. But a software firewall needs to be enabled.

Some people on the forum feel that this points to spyware or viruses on the user’s PC. I have scanned my PC and found no traces of spyware or viruses, so this may be a problem with Firefox.