networking issues

i have an issue that's been happening more often lately. i'm on mac (G5 dual 2.7, 10.5.2) that accesses shared clients on a windows network. more often than not, i have no problem mounting those clients, but sometimes my mac seems to decide to just "stop looking". when you go to mount a client that usually mounts instantly, it will just hang there as if i weren't connected to the network. even when i already have other network shares mounted from earlier. those shares work fine, i just can't mount anything else. the fix is fairly simply though inconvenient. all i have to do is log off and log back on again. it seems like it gives the networking a wake up call. by the way, this also effects communication between the other macs. mounting mac drives from the other macs in the department as well as screen sharing just doesn't want to work without relogging in (which means closing all apps). is there a way to give the network a refresh, for lack of a better term? i don't know why it's happening, which is also frustrating.

any ideas would be appreciated.
thanks