Windows Explorer hanging when browsing network drives

I have some XP SP2 64bit systems that are having a couple of Windows Explorer
issues.
-- When you browse a network drive and you are traversing up and down
the tree the Explorer window will display the next level of the folder
structure. You get the flashlight and a searching for items in the status
bar. After anywhere from 30 seconds to 2 minutes the window finally
populates. You can kill the explorer.exe process and restart and the
browsing ability will return for a short period of time.
-- When in My Computer I can right click on a mapped network drive and
select properties. However the properties never are displayed. Right
clicking on the C:\ drive and selecting properties works normally.

Any idea?