[phazed]

Assuming you haven't fixed the problem with the others suggestions...

Have you tried to use a different computer to ActiveSync with? Perhaps your USB on the PC is getting flaky.
Unrelated to phones or storage cards.. Once upon a time I experienced USB problems with certain USB devices. A standard USB mouse would work.. but a Wireless keyboard and mouse set wouldn't. Turned out to be the power supply going bad, supplying unclean power.

You said you installed ActiveSync from the CD again to try and correct the problem... My general rule of thumb is to never install Device drivers/software from the CD.. as there is usually a new/updated/fixed version on the internet. Maybe try downloading AS from Microsoft.

Its odd that the computer won't manipulate the data on the card.. which is why I suggested your USB is flaky.. but maybe it's the card. Have you tried to boot the phone WITHOUT the card inserted? Perhaps the card is corrupt/damaged and this is why the phone is unresponsive(Trying to access a bad card), and it can't be read on the computer.