I had this issue with build 7057 the first time I installed it on my desktop. Eventually everything started hanging up every 8-10 seconds. I spent a good 45 minutes trying to figure out the cause, gave up and reinstalled. It never happened again after the reinstall, so that's probably going to be your best course at this point. With a beta OS you have to account that there will sometimes be weird issues like this and be prepared to reinstall everything because of it.
If you installed 7068 you don't have much time into it yet so I'd just wipe the drive/partition and reinstall. Just my $0.02.