Tracking down the issue involves ALL pieces that make Moodle go ... PHP, Apache, and MySQL. Since it's Bitnami Stack have you checked with their forums to see if other Bitnami users are experiencing the same? What versions of everything does the Bitnami Stack install?
This one??? http://bitnami.com/stack/moodle/README.txt
Since APC was install recently, have you found that apc.php of which I spoke and installed it at document root of apache server yet? Seems to me the logs for apache might have a 'failed to allocate' error if APC runs out of memory that's been allocated to it ... 64 Meg is default for it. Moodle 2 will eat that up in a hurry just accessing the site. 128Meg is a good starting point - but that's if there's enough memory to allocate that much.
So no clues in apache, php, mysql logs at all?
So what does your apache config file look like? What does your my.cnf (my.ini in Windows terms) file look like?
There's a tool for Linux boxen called mysqltuner.pl. But requires perl and going that route with a Winders machine means more non-Microsoft apps installed. Could try a beta of it for Windows:
Comment (question to research and food for thought): IF one does get the bitnami stack running and when Moodle makes a security announcement that should prompt you to upgrade, how easy will that upgrade be? That could be true of Apache, MySQL, and PHP separately also. Can one upgrade (easily) say Apache separately or does one have to download the latest release of Bitnami package ... which means touching all the pieces. Easy button install is sometimes the tip of the iceburg when it comes to maintaining.
'spirit of sharing', Ken