With MBAM Pro running you would be best to exclude the complete folders of avast and MBAM to save on each from scanning one another, you'll also find that if you turn MBAM off your system will spring back into action again as Malwarebytes will be what is using the most resources on your system, the 1.75 version was a lot heavier than previous version and the new version that is alpha stage at the moment is twice as heavy on resources again.
Try disabling MBAM from starting with windows, you can have it set to update and scan once a week for piece of mind
Hmm, I have the same on any system I install avast to, I always turn off " scan when opening", it is avast that kills the system.
I have tried this on Win7 and Win8, shutting down MBam makes zero difference.
Win7 64Bit Dual Core and 8GB Ram ..... with Scan when opening is it on cripples documents folder and program list , This Computer and Network , no MBam running, turn off that avast setting, , run MBam as resident, and the folders open instantly.
My neighbours machine has an AMD 8Core and 16GB Ram , he has AIS9 no MBam, the same thing happens.
I turned off the scan when opening years ago, avast and MBam run fine and I have had no malware/virus issues. The system is already scanned in realtime , and when anything is written.
On my Win8.1 Pro laptop, Bitdefender, Panda Cloud, Avira, and Trend Micro have been tested, none of them have this impact.