In Media >Options What are your memory limits set to?
Check "Device Memory Limit" and "Reserved Pictures Memory."
I'll say this again....Get a Media Card. You WILL have problems at some point when you store media files on the BB. Media cards are SO cheap these days. You can get them at NewEgg.com for next to nothing. I'll bet you can find 4Gb for under $20 and probably closer to $10.