What should i do?

Hello,

So pretty much my virus protection "Eset Smart Security 5" is displaying a warning message about 10 minutes into launching firefox saying

"Operating memory » firefox.exe(2260) - probably a variant of Win32/TrojanDownloader.Mebload.AR trojan - unable to clean"

Firefox is also becoming very laggy.

What do you guys recommend i do since eset is unable to clean it?

ps: Already tryed reinstalling firefox.

OS:
Windows 7 Ultimate 64bit