Mac AppStore Resume Issue

I'm using Mac App Store on Lion, But there is a problem with download resume. After every system restart I can't resume my previous downloads and I have to download them from the beginning, I also checked and I have no AppStore directory at this path ~/Library/Application Support/ AppStore store the temp files at a directory in /private/var/folders/s1/ ... /com.apple.appstore/ But after restarting the computer and opening the AppStore it deletes all the contents of this directory, and I have to start the downloads all over again. I also tried restarting AppStore in debug mode but it didn't work. I'm wondering if someone have a solution for this issue. Regards