I'm not really sure this problem is caused by avast, i've test several computers and always got the same results.
Environment: Win7 64, avast free 6.01
Problem: When i try to copy a large pdf file to a usb storage media (not include usb harddisk, problem arise for cards and u disks), the copying progress bar would pause at some point and remains for a long time with a speed of zero (sometimes several minutes), actually the new copy is already created completely. When i disable avast shields, this phenomenon disappear. And this only happened for pdf file and usb storage.
Use "Process Monitor" i found that in such cases, the operation of the "IRP_MJ_CLEANUP" consume an unusually longer time.
Could anyone tell me how could such thing happened? Any advice will be appreciated.