I'm not sure whether they're related, but I also just noticed issues... 'cannot display...' errors on checkout and blank shipping estimate pages. Disabling the AustPost module fixed it, however I believe the problem lies with the Australia Post DRC Server as I notice the following line in my Error Log:

[17-Nov-2007 14:07:23] PHP Warning: file(http://drc.edeliver.com.au/ratecalc....amp;Quantity=1) [<a href='function.file'>function.file</a>]: failed to open stream: Connection timed out in /home/.../store/includes/modules/shipping/austpost.php on line 611

That said, I justed doing some research and noticed your post. I recall a thread on the line 611 error before and will continue to look for it and its answers ;)

Cheers
GAM