First thing I would do...is disable all browser add-ons.
Then...I would go to the appropriate website for installing Flash Player...and install the latesst version.
I would alos take a look in Event Viewer...to see if the errors reflected there can point the way to suspects.
Funny...you don't mention at all running your installed AV program.
Rkill doesn't remove malware...ComboFix is a specialized tool for dealing with malware and is not guaranteed to reflect a clean system (the BC Malware Removal Team does not use ComboFix as one of its tools)...and Malwarebytes is an application devoted to removing various forms of malware. None of these programs is perfect with regard to removing malware...that's why the MRT here uses a variety of tools to try to assist.
Neither of these programs should be relied upon to do the work of an AV program, xine their purposes are totally different. Removal is not the same as prevention/protection, IMO.
In short, I would not rule out the fact that your system is infected. But I would try the suggestions made above before moving to that possibility.
Edited by hamluis, 21 February 2011 - 03:05 PM.