I am having a similar issue but not exactly the same. When running an mbam scan on the c drive, the system locks up for about 4 seconds and then is available for about 1 second. The pattern repeats until I get lucky clicking the pause or abort buttons. Usually I've had to end task mbam to stop the issue. The mbam process is taking very little cpu resources when this occurs. Interestingly, the d (sata) and e (usb) drives scan at normal speed without issues. I tried running mbam with and without avg8 running. The fact that only the c drive is an issue tells me it probably isn't another process causing the problem. About two weeks ago I ran mbam for the first time, scanning all drives without any problems. Do you want me to give the debug freeze a try?