This occurs in all versions of Vegas when there is memory loading that affects the audio buffers.
It can occur when there are lots of tracks, when there are effects, at higher audio bit / sample rates, or if your drivers are exhibiting high latency.
Switching to ASIO drivers in Vegas and closing down other applications that use memory helps. Keeping your playback at 16/48 while previewing also helps.
Also, occasionally saving, closing, and re-opening your Vegas Project can help, as that dumps the memory buffers being used by the program.
No, you didn't miss it.
He didn't mention what sound card he has and his systems specs in his profile are blank :-(
It would be really handy for all users to fill this out as it would help troubleshooting.
I understand that some users have more than one system but please put at least one system spec in there.
Even better is to mention what specific device(s) you're using when you're talking about a hardware issue.
"err.. guys... asio drivers will ONLY work with asio HW"
Once again, someone has posted something on the Vegas forum which is incorrect. People come here for answers and a portion of the information on the forum is dead wrong. Folks, if you're not 100% certain about what you're about to post, then don't post it.
"ASIO4ALL is a hardware independent low-latency ASIO driver for WDM audio devices. It uses WDM Kernel-Streaming.
In order to successfully run ASIO4ALL, you need:
A WDM-compatible operating system, such as Win98SE/ME/2k/XP/2003/XP64 or Windows Vista x86/x64.
A WDM-driver for your audio hardware. (Under Win2k/XP/Vista... this is implicit, not so under Win98SE/WinME.)"