WorldEdit 1.32 changes a Registry entry that doesn't play nice with the older versions of the editor. I've documented it extensively and submitted it to Blizzard, but this is unlikely to get fixed by them since they don't want people doing this in the first place.
World Editor versions issue with Windows Registry
Full path of key located at HKEY_CURRENT_USER\Software\Blizzard Entertainment\WorldEdit
The key in question is called “Tool Windows” under “WorldEdit”. The value the 1.32 editor changes this to will cause any older version of WorldEdit to crash when this was not the case prior to the last patch.
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What I ultimately did was make a .Reg file for what the value of "Tool Windows" should be for 1.26 and apply that whenever I need to use the older editor again. Every time you run the 1.32 Editor again it changes the value back.
I can't post the actual file because of various reasons, but this is its contents more or less:
[HKEY_CURRENT_USER\Software\Blizzard Entertainment\WorldEdit]
"Tool Windows"=hex:00,00,00,00,01,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
80,06,00,00,00,00,00,00,80,07,00,00,e3,03,00,00