Mail hangs when dragging *anything* into Dock Icon

Hi, I have an odd issue. I rarely use the mouse to perform drag & drop operations, as I use quicksilver most of the time, however, from time to time, I just "drag" pictures (screen captures) to the Dock Icon of Mail to quickly send 'em over.

I have mail open 99% of the time so it's running. Apart from the odd "duplicate message" that I got used to, something strange started happening lately. I found this out a few days ago but didn't do anything until today where I tried to find a solution (without success).

The thing is, I drag a picture (or many) or a chunk of text or whatever you imagine, to Mail's Dock Icon. Automatically one "empty" message is created (as usual since Leopard) and then, when the second window appears, it remains empty and spin ball appears. I have to force quit Mail.

Things I've tried:

- Reindex Mail (removing envelope). Not fixed.
- Reboot (of course!). Not Fixed.
- Try with Mail Closed or Opened in advance (same results).
- Read the logs: Couldn't find anything interesing and/or related.
- Submit crash reports: did it at least 10 times.

I've run out of ideas. It's very annoying because I happen to do that from time to time... :S

Other details I've found after further inspection:

Mail appears to enter into some sort of LOOP. Because RAM starts growing and growing until no ram is left (2GB) and therefore, Swapping starts. Taking a look at Activity Mon shows exactly that.

Any pointer that could give me a hint where to start?

I'd appreciate that, thanks.

P.S: I have enought HDD space left (7gigs), I've tried with a cold reboot, open mail, drag. Same result. I haven't repaired permissions (but will try, tho I have the feeling that it doesn't have anything to do).
I don't know exactly when this started, but for sure it used to work "a few days ago".

Thanks in advance.