Installed 5.0B...working well, but was still finding a few random, subtle pops and crackles. After uninstalling, going back to 5.0, and back to 5.0b again, I found that I had forgotten to go to Preferences and route TEMPORARY file storage AWAY from (vegas default) Active (C) partition, which doesn't have more than 900mb of free space. Once I changed that setting over to my E drive, where all the wavs go and has many gigs of free space...the crackles went away. I hope this helps in the quest for peace and quiet.
P