When I look in the console I get this message
2010-09-18 17:04:05.284 Wasted Time[8998:207] *** Assertion failure in -[UIActionSheet showInView:], /SourceCache/UI
For those like me that may be using UIActionSheet slightly differently than in the original question, but still failing on iPad, I had been using:
[actionSheet showFromRect:m_view.bounds inView:m_view animated:YES];
[actionSheet release];
...which works on iPhone but fails on iPad.
This example works in my particular app on both devices:
[actionSheet showInView:m_view];
[actionSheet release];
Regards, David