I had the same problem when running Squeak on Vista. It turned out that it was due to NOD32 anti-virus checking the changes file when it was written to. Disabling the .CHANGES extension in NOD32 fixed the problem, and now Squeak runs fine.
Cooool.... really coool
This is it... Thanks a lot Andrew, you solved the problem that was hassling me for weeks... I owe you a beer ;) I actually had an equivalent problem with XP (slow snapshoting method) still due to NOD32 ... as it'is the common point between my 2 systems ! So, we need to be aware that NOD32 (AMON-Access scanner) interfere with the changes files !
Thanks again Cédrick