Thank you for your post.
I am unable to replicate the problem with FileMaker Pro 11.0v2 running on Mac OS X 10.6.6:
1. I open a database file with 40 tables and 46 layouts.
2. On one of the Layouts, I add a Portal, select the "Show related records from:", and I'm able to use Page Up, Page Down, Home and End keys, and the selection jumps to the first and last entries (depending on key pressed).
3. On the Layout drop-down, I can use the same keys, as well as alpha keystrokes to move to the appropriate selection.
Let me know what I'm doing differently than you, and I'll try to replicate the problem here.
I have seen this behavior come and go intermittently. I think it might have something to do with having FMPA 10 and 11 open at the same time, but I can't swear to that. Thanks for checking into it - I will try to narrow down the circumstances in which it happens and let you know.