I'm afraid screenshots wouldn't be too exciting or helpful in this case...it was just an error saying that that Windows couldn't determine the helper program for .PLT files. After running traces with Procmon on a working system and a non-working system, I was able to get my test system working by importing the following keys from the "good system":
[HKEY_CURRENT_USER\Software\Classes\.PLT]
@="PlotFile"
"Content Type"="application/vnd.hp-HPGL"
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.plt\OpenWithList]
"a"="iexplore.exe"
"MRUList"="a"
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.plt\OpenWithProgids]
"PlotFile"=hex(0):
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts\.plt\UserChoice]
"Progid"="Applications\\iexplore.exe"
This seems like a clumsy fix/hack and I'm looking at SAP for being the bad guy. Why doesn't it understand/look at definitions for .PLT in HKCR? If I can open a .PLT from Windows Explorer, SAP should be able to do the same. Thankfully, we won't be putting .PLT files in our new SAP implementation, so hopefully I never have to deal with this problem again.
Thanks.