win2k - win2k file directory content update f5 issue over ..

We have a very large, busy wan (ATT MPLS) network with many sites fully
meshed connected, with many servers connected with AD. We have many drive
shares with various share arrangements between 2k3 - xp, 2k3 - 2k, 2k-xp, and
2k-2k. Everything is working, but...

2k-2k drive sharing is the problem. While the connection maps properly, the
directory contents does not list at all, until the f5 update key is pressed,
then it is listed correctly - for that folder in the drive share. File copies
from this drive share appear to tranfer at normal rates.

Peforming a dos "dir" exhibits the same behavior. The same win2k server
mapping to a 2k3 share or a xp share, does not exhibit this behavior - even
using the same wan path and utilization rates. Only 2k-2k drive shares is
affected.

We tried various 2k servers at different sites - same result. Sometimes it
appears to work, when the wan is not heavily utilized late at night - but not
always.

Question - why is 2k-2k file shares more sensitive to this over other type
of shares. This started about 2 weeks ago, - trending indicates no
configuration or utilization changes on the network. Comments, please. The
only bad idea is the one left unstated...

Thanks, in advance. Jim