I was having this... uploading files directly to my 1GB lexar card. Every time, when a certain file size was hit, scp would stall and usbnet would lockup. I'd have to unplug the USB connection, wait a while, the replug. Seemed to happen somewhat at random when over 7.5MB have been copied..
In a flash of inspiration, I realised my card was formatted FAT, not FAT32 (because I used it in my Palm T3 originally). Copied all the files off, reformatted FAT32, and restored everything.
Guess what?!!
...
Didn't make any difference.. it still locks up.
I worried that it was related to my similar problems with bluetooth, whereby a heavy network load locks up bnep0 networking.
This is running SuSE9.2 + kernel 2.6.12.1 on the desktop, Cacko 1.22-full on the Z.
NOTE: I don't get this problem when copying to normal memory on Z i.e. to /home/zaurus.
Paul