Thanks for trying a new profile and confirming that it doesn't help.
I don't think it's a matter of you and @kitaro1 being ignored, so much as the fact that no one here has a solution to the problem. I haven't tested it, but I strongly suspect "official" Pale Moon and Basilisk (on Win 7+) will have the same issue. I seriously doubt this is a bug that both @roytam1 and @feodor2 have both independently managed to introduce into their respective PM forks.
So unless @looking4awayout's UOC patch helps, we're at the mercy of MCP to come up with a fix. Unfortunately the browsers (that @kitaro1 mentioned) that don't have this issue with GMail simply don't run on XP (or Vista), and can't be made XP-compatible.
If that's the case, you know the drill: confirm the issue with official PM on a supported OS (Win 7 or later) and report it to MCP directly via PM's Help / Submit Feedback link.
I agree; this has bitten me too when trying multiple versions of, say, Firefox, on the same PC. @VistaLover has the right answer - install at most one non-portable version of each browser - but it's easy to forget and not always practical.
Luckily some combinations do work: Basilisk/Serpent 52, Serpent 55, PM/NM, BNavigator, Seamonkey, and FF all use different profile folders, so one of each of those can coexist peacefully without using "portable" versions.
That's a bit much to ask of, say, 7-Zip; how's it supposed to know that what you're unzipping is a browser with this particular potential issue? But I'll look at adding a message of that sort to my "Download Latest Browser" batch file.
AFAIK e10s/multiprocess only works on FF and Serpent, not NM; trying to enable it on NM just crashes it. But @roytam1 is customizing NM by locking some e10s-related preferences, so inadvertently installing the "wrong" UOC patch from @looking4awayout won't crash the browser.