In files.xml is saved the tree, order, and some properties of C# files. If the old portable files.xml == non-portable files.xml (or very similar), then the portable workspace is still valid.
But some dlls in the \dll subfolder now may have wrong versions, and it could be the reason why now portable LA crashes. Try to delete the portable \dll folder.
But some dlls in the \dll subfolder now may have wrong versions, and it could be the reason why now portable LA crashes. Try to delete the portable \dll folder.