It might be helpful to also know the exact cause, before you pick one of these solutions. I recently had this same issue while trying to synchronize files from a Windows 2003 Server to a Windows 7 workstation. At random, the server would lose its connection to the Win7 box, and attempting a NET USE command to map a drive would return a Status 58 like this.
Rebooting the Win7 box would fix it, but this seemed drastic. Looking deeper with Wireshark, we found that an SMB request was going to the Win7 box, and an SMB reply "Out Of Memory" was being returned. Stopping and restarting the Server service on the Win7 box resolved the problem, at least temporarily, and is much better and faster than a reboot. I expect that the registry changes for the large system cache will resolve it completely, but these changes may not be suitable to a permanent change, just to get past a temporary issue.