NT Login Script Error

get rid of if errorlevel 1 goto Plantops doesn't make sense.

Thanks for your prompt response!

I tried both suggestions:  added ifmember domain\plantops, did not make a difference.

I also removed "if errorlevel1 goto PLANTOPS"

Still getting same result:  
Bad command or file name
Syntax error

The error is probably in line 14, "if not errorlevel1".
That aside, you have two labels ":PLANTOPS", and the result checking required some changes.
Quotes are only required if the group name contains a space; but it's a good practice to add them anyway, so that you get used to it.
The script below should pause at the end, so that you can see error messages.
ifmember.exe is in the same folder as the script?

"%~dp0ifmember.exe" "PLANTOPS"
if errorlevel 9009 (
  echo ifmember.exe not found in %~dp0; leaving the script
  goto Leave
)
if not errorlevel 1 goto MAS500_Reports
net use p: /delete > Nul:
net use p: \\mystique\plantops
Echo Drive P is mapped to \\mystique\PLANTOPS
 
:MAS500_Reports
"%~dp0ifmember.exe" "MAS500_Reports"
if not errorlevel 1 goto Warning
net use u: /delete > Nul:
net use u: \\gf-finance\mas500_reports
Echo Drive U is mapped to \\gf-finance\MAS500_Reports
goto :Leave
 
:Warning
call \\cartman\netlogon\warning.bat
 
:Leave
pause
                                              

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I copied the code you wrote and tried it again.  Now I'm seeing the error -
Bad command or file name
ifmember.exe not found in ~dp0; leaving the script
Press any key to continue. . .

What does ~dp0 mean?

Oh and yes, ifmember.exe is in the same folder as the script.

I just copy and pasted the script from this post so it should be exact.

I have the script on both NT servers in the Netlogon share.  I was testing 2 ways - via login and just opening the batch file.

The first OS I was originally testing on was Win98 - when you asked what OS I then tested on an XP machine.  The XP machine mapped the drives for both groups, even though it was only a member of the plantops group.  

ifmember IS in the same folder as the script.

I tried running ifmember.exe /list on the xp machine and it couldn't find the file, because the file is only on the nt server.  So I copied the ifmember.exe to the XP desktop, ran the /list and the appropriate groups displayed.  Then I tested again by logging out and back in again and it worked as expected!

So - do the desktops also need a copy of ifmember.exe locally? (I copied to windows\system32)

Having it in the script's folder should work, at least for XP/W2k; that's what the "%~dp0ifmember.exe" does.
I have no idea whether ifmember will run correctly on Win98. "%~dp0" or anything else that requires the NT shell instead of the few plain batch commands DOS supports won't work for sure.
If you really want to support a DOS based OS in a logon script, have a look at Kixtart (http://www kixtart.org/) instead. This allows some sort of compatible logon script that should run on both OSs.