net use print jobs freeze PC whilst transmitting

I have a small peer to peer XPSP2 network with one PC acting as a print
server. Client PCs have each printer setup as local machines on LPT1 through
to LPT9 and I use persistent net use commands to map each LPT port to its
associated UNC share name.

This all works well except that whilst the print jobs are being transmitted
from the client print spool to the server print spool, the client PC freezes
until the print job has transmitted. If I work offline I can generate the
numerous successive print jobs, but as soon as I go online the jobs transmit
and the PC freezes.

My searching of the KBs and the NGs has yielded no insights. It is as if the
net use redirects are set to "realtime" priority on the Task Manager. Any
help would be appreciated.

Regards
Malcolm Dowers