UNC Paths not supported.
Part of this issue seems to have been with the servers NetBios after an update. I changed it a couple of times and debuged scripts. Search UNC Netbios for additional information that might help you.
If you've attempted the NetBios and know your scripts are perfect then read this article here for what might be the fastest and easiest method.
(I know this post is out of order in that I've edited it a few times and will detail the troubleshooting steps at a later date.)
1. Be sure your scripts are running dispite the error.
REG ADD "HKCU\Software\Microsoft\Command Processor" /V DisableUNCCheck /T REG_DWORD /F /D 1
HKCU Software Microsoft Command Processor DisableUNCCheck REG_DWORD 1
But, like anything that has been working and then stops working you have to wonder what happened.
Disabling the error message might be all it is, but only if you are seeing the drives and scripts running correctly. If not, send me a link to your scripts and I'll see if I can help.
end edit 5-8-2012
I have seen this when the Active Directory do not set the users permissions correctly during login.
After a security update to the SBS 2003 DC and AD I started seeing this issue.
I thought I had the correct notes handy when I started this post but it appears I have the troubleshooting steps that don't show the solutions I found.
I do know the scripts had worked just fine for for months and I had to rework a registry entry to make the UNC error just stop. I believe it's the one referenced in this article.
The Drives would map if you check you might find yours as well. It would just display this error and confuse the whole issue.
As Admin you shouldn't see this error. Standard users seemed to be the only ones. Again, that points to permissions more than script issues.
I was working older XP's with SP3 installed. But I also saw this error on a SBS 2003 Terminal Server on the same network.
I believe it was a Microsoft Security Fix that caused every connected workstation to start showing UNC path errors.
CMD.EXE was started with the above path as the current directory.
UNC paths are not supported. Defaulting to Windows directory.
The fix right now elludes me but I do remember working with the global policy and local machine policies with no luck.
I even rewrote the Vbs scripts and still nothing.
It wasn't until I started seeing even more problems that I recovered the OS from an Acronis backup and reworked things that had been completed for months. Aronis SBS2003 Backup was used and as always it showed just how easy life as a IT admin can be at times. The real work came when the DC needed to be reconfigured for the network.
Basically I saw a permissions issue and after fighting with it for 4 days I had no choice but to recover the OS.
I'll review my notes and post most all the things I did so you can give them a try. Guess our key to having a good recovery backup system paid off for us this time but still the UNC Path issue after a hot fix is mind blowing how it could have hammered that SBS2003 so hard.
I have the old DB open 5-8-2012 and will dig up the solution or I'll post up the full login script and start looking over the UNC issue. It was a pain.