PM editing error

[Mefista 98]

I had written a message and, right after sending it out, noticed that half of it ended under spoiler (my bad, probably didn't wrap properly). Went back to editing (3 minutes later), and it refused to let me save edited version, citing this:

Not the first time that happens, by the way. Is the message lenght or anything else to blame?

[Woodus 1,465]

Possibly, we ran into that error with a post that had a bunch of images, I cannot find an image limit or post length setting but that is what it seems to be.