LA 2202: Out of Memory - What does this mean?

I get this message all the time.  If  I restart the PC, it makes one backup successfully, then I get the error on the next one.  What the heck does this mean?  What memory?  I have plenty of backup space.

 

Win XP SP3

Pentium 4, 3.0GHz

2.99 GHz, 3.25 GB RAM