Body of a post gets truncated after editing

I've noticed a strange thing.
I make a post, which contains an emoticon. When I edit the post, everything after the emoticon (including the emoticon disappears).

Now I'm going to post 2 replies, with the same content, and I'll edit the second so you can see what I mean.

This is the first line [img=/images/smiley/msn/teeth_smile.gif][/img] .
This is the second line .
The second post will be the same, and I'll edit it later.

This is the first line

Possibly related, some very long posts clearly have the ends missing. EG: They're a list of rapidshare/mediafire links and the post ends halfway through a link halfway through the list.

Oh, and double-posts keep happening [img=/images/smiley/msn/tounge_smile.gif][/img]