@mark_m – it's the external hard drive. This issue has come up from time to time before (it's not specific to the beta), but I've never been able to repro it.
Some questions.
1) What is your main hard drive letter? Is it C:\ or something else
2) What letter does the OS assign to the external drive when it mounts?
(
@Armando, It's a windows issue only.)
Best Wishes,
Mark