Are your memory cards accessible? I've got 128MB of virtual memory on the internal card but the N800 gave me memory errors, too. The problem is the N800 loses connectivity with BOTH of my 8GB SDHC Class 6 Transcend memory cards "every so often" and for no apparent reason. The cards are fine. The OS2007 upgrade is successful. It doesn't scramble the cards, it simply stops talking to them.

Nokia was no help. "Those are not Nokia memory cards." and "The N800 only supports 2GB memory cards." was the answer I got after being on hold for "research". I knew I was in trouble when the support guy said it might be a hard drive problem....(c;

The solution is easy and simple but frustrating. Do a normal shutdown. Remove the battery. Count to 5. Replace the battery. (Make sure the chargers aren't connected!) ...and boot up again. All memory cards are back in action until the next time the bug in the boot ROM appears and dumps the cards, yet again.

Once the cards are back online, the memory errors stop as it's using virtual memory, I suppose, it couldn't find before.