There are 33350 line in my magit buffer. I typed tab to collapse my "untracked files" section, and my emacs hang. cygwin 1.7, emacs 23.3.1, magit 1.1.0 in elpa. My hardware is pretty good, btw.
Are you sure it was hung (I mean, as opposed to just taking a long time).
Did hitting ^G have any effect?
What did you eventually do to stop it?
I wait for several minutes before killing my emacs in windows task manager.
I tried ^G before killing.
My pc is 8 core, 12G memory HP work station. So it's not normal to wait several minute to expand "untracked files".
I put my home directory under git control, so there are 30K untracked file under that repo.
Please reopen if this is still an issue.