Have you tried testing your expression in another regular expression parser to see what happens?
I tried it using Expresso (which, basically, returns the correct values). I don't know if there is a "more advanced" expression parser available anywhere, so far it was enough to me. (Any ideas?)
@Zed: ... that works!
Thanks! Now
that made so much of a difference?
Working regex:
/<img([^>]*)alt="([^"]+)"([^>]*)(\s)?(\/)?>/g
EDIT: I was told it still crashes. :-(