Ok this problem is kind of weird....

First off Firefox is my default browser, now when i'm on msn and someone sends me a link, normally clicking the link once in the chat window would launch my default browser (Firefox in this case) and go straight to that link location.. but for some reason... if i just click the link once, my browser does not show up, BUT it does appear in the processes.
Also id like to note that... well... lets say it was a link to a youtube video, well i would in fact hear the video play, but no browser window would have appeared.
My workaround was to double click on the link, obviously giving me 2 tabs of the same link, but allowing the browser to appear..
Strange thing is that i have two pcs (1 desktop 1 laptop) both running windows 7 ultimate x64 with firefox (latest) and msn (latest), this problem only occurs on my desktop pc, laptop works as intended.
what could be the problem

oh ya also running McAfee Antivirus 8.7i Enterprise Patch 2 with Antispyware , Malwarebytes' 1.46 Database version 4199
PC Specs:DesktopWindows 7 Ultimate x64 ASUS OEM
Intel Core I7 920 @ 3.6GHz
ASUS Rampage II Extreme Bios 1639
12GB DDR3 1600MHz LaptopAcer Aspire 6930G
Windows 7 Ultimate x64 ACER OEM
Intel Core 2 Duo T9600 @ 2.8GHz
4GB DDR2 800MHz