Its quite possible that the malware or what ever you want to call it is stoping Mbam from picking it up... Download Rkill.. and run it up in safe mode and the hit ur pc with a full system Mbam scan, and after the mess is almost cleaned slap it with a Combofix too..
Double check that your Mbam is completely up to date too..
never kill files like that if you dont know what they are
many viruses are like barnicles they attach themselves to system files to make themself's hard to remove without a bootcd or a good antivirus
go on repair file if that option is availble
why not try a program that stops viruses infecting like a hips (host based intrustion prevension system)
one i recomend is comodo, there is a steep learning curve at first but after a while it dosnt even alert you at all and makes your computer much safer (its like everything it may be much more secure but that dosnt mean its impossible to get viruses)