Mysterious GET request in Apache

I've been getting a couple of strange GET requests on my dev server from unknown IPs. I don't know if this is some weird character encoding or something entirely else. The mysterious thing is, my server responds with the status 200, so the input matches something, but I don't know what.

The request is ":\xcc\x89\xa9L\xcf\xc3\xb6\xc1\x8f\xa9\xe7\xc0\xec\x16"

Ideas?

EDIT: Corrected the request, it wasn't a GET request, but still returns the root index page.

EDIT2: A new one just popped up:
xxx.xxx.xxx.xxx - - [20/Oct/2010:09:10:33 +0300] ";\x8e\xb0!\xa2\xa7\xe7\x11\xf1HX\xb6\x188|z\x9b\xac;z\x10\xafn\xd8*fD\x9d\xc1\x11I\x9a5\xe6\xcbu,\x8c\xd7\x84O[\xf7\xca\xe67\xe5\xba\x94\xdd.\xc0d\xd0} " 200 2085 "-" "-"
Nope, definitely not unicode anymore...

Maybe a WebDAV hack similar to:

http://www.sans.org/security-resources/malwarefaq/webdav-exploit.php

Trying to exploit a buffer overrun.

It could just be someone attempting to exploit your system. What is your server's response to the request ?