I just started using the aqua-soft skin on a vBulletin site running v. 3.6.7 and I've been able to verify a crash. In fact, the crash occurs even on this site. Some of the time it doesn't crash completely but the window locks up, no other links or buttons work.
I've pinned the problem down to the search box (Search Forums), why it happens and what you might want to do about it.
On the Safari browser, when there is default text in that search box, Safari puts up a small graphic "X" designed to clear the box of text. You are using an onFocus javascript to clear the box as well.
If someone clicks on the "X" to clear the box, the onFocus tries to run at the same time. This seems to cause a race condition.
If you switch to an onClick statement, the crash will not occur.
Aqua-Soft Forums