I have:
GO910, b/l 5.5229, Nc 9.053, map W&CE 856.3245 and, normally, 13-10 GB free RAM and all works fine - I connect to TTHome once or twice a week for mapshare and GPSFiIX updates.
Spent 10 days touring France (many destinations/vias) and free RAM frequently dropped to <2GB and GO became so slowww redrawing map view and planning any Navigate tos'.
A 5 second pin reset freed up RAM, for a day or two. ...