rtl8139 trns timeout after short OK in Karmic and Lucid

A mobo RTL8139 family NIC using the 8139too driver on a core solo machine hangs after a short bout of doing routine network traffic. dmesg gets a whole string of

[ 6529.872029] CIFS VFS: Unexpected lookup error -112
[ 6535.000082] eth0: link up, 100Mbps, full-duplex, lpa 0xC5E1
after a bit of making a local backup of the NAS.

in syslog, I see some of

kernel: [ 5308.000059] NETDEV WATCHDOG: eth0 (8139too): transmit queue 0 timed out

ifconfig shows a normal connection. ifdown -a returns no problem, ifup -a hangs,

This was not a problem with 9.04 but does occur with 9.10 and the Lucid Alpha. It requires a power off reset to be able to use the network again. I do have W7 as a dual boot on this machine but seldom boot that. I have bios boot from NIC turned off. I am planning tests to see if this only happens with heavy local loads like the NAS backup or if I can get it to happen with I'net CD image backups. I was able to do an inplace system upgrade from Karmic to Lucid alpha via network without having to do a poweroff reset to complete.