Originally Posted by fpp

It's power-saving all right. I had something similar on my 770 under OS2005 : I could not usefully ssh from the PC to the tablet because battery management would kick in during pauses and the Wifi would go into a sort of "sleep mode", although still connected. Incoming data would not wake it up, only outgoing traffic from the tablet itself would.

Others has the same symptom, but strangely enough with varying degrees of gravity - from mere annoyance to unusable (in my case).
Some solved the problem by streaming music or other stuff to the tablet to keep the Wifi alive during the ssh session. Through trial and error I found than opening an xterm and pinging an external host every 4 seconds was enough. But not every 5 seconds :-)