The trust relationship fails

I know that there have been a few questions re this issue but no answers that
seems to meet my situation

Scenario - (Brand new install)
Server 2003 R2
HP Thin clients
Attache accouting software running in terminal session
Serial docket printers attached to thin clients via USB to serial converter.
These printers are also shared on the network so appear on the server as
shared printers. These printers are then used in the terminal sessions to
print from attache.

Problem 1 (Main problem)
Within 7-10 days of the thin clients joining the domain, their printers
(shared across the network) stop responding. Investigation reveals the
following:
The printer on the thin client shows as "unable to connect"
Trying to connect to the thin client via \\pcname returns an error to the
effect that "...The trust relationship between the workstation and the
primary domain failed etc etc"
The thin client can be pinged via ip address and PC name no probs
The thin client still connects to the server via terminal session and runs
the app without any errors
Event log on the server shows nothing of note
Removing from domain and rejoining will "usually" work (as suggested by
others) however I have already done this 3 times in the last month so there
is obviously a deeper issue.
I replaced one thin client with a USDT and have had no problems since.
Any ideas/solutions?

Problem 2
The docket printers tend to just stop printing or opening the cash drawer
for no apparent reason at any given time. One minute they are fine and the
next transaction - nothing... Sometimes a reboot will help but not always. It
has been suggested to lose the old serial printers (on usb converters) and
get new parrallel docket printers as Parrallel printing works better in TS
than USB/Serial. Every few days there is a different issue to the last. You
fix it and then another issue that has been seen before pops up. I am
beginning to suspect the serial to USB thing is a head short of a herd and so
throws weird errors.

Would appreciate collective wisdom on these issues.
Thanks

Billy Gareth