Can boot into recovery through RM, but SD card won't mount

Here's my issue: I can download ROMs OTA, and then am able to boot into recovery, problem is that the SD care never mounts and it just reboots without installing anything.

1. I am able to hold down "x" and manually install zip files from the SD card, so I've been just putting them into root via my computer.

2. This is the second SD card I've had, the first was about two years old and finally was reformatted into oblivion.

3. I've tried uninstalling and reinstalling ROM Manager, as well as flashing alternate recoveries, still no luck.

Any suggestions?