That sounds like a huge problem! I definitely want to get this resolved so you can have the best experience with this device. It almost sounds like this could be a software glitch on the device where it isn't reading the memory properly. Have you installed any new applications recently? They may be causing problems so I'd recommend uninstalling them to test if they are causing the problems.
The next step would be to check for any software updates. The latest build version for this device is T859UVKJ3. If you don't have the latest software, you'll need to complete the Software Update: Samsung Galaxy Tab 10.1.
Let me know if this helps!