Wirelessly posted (iPod touch 32GB: Mozilla/5.0 (iPhone; U; CPU iPhone OS 3_0 like Mac OS X; en-us) AppleWebKit/528.18 (KHTML, like Gecko) Version/4.0 Mobile/7A341 Safari/528.16)
That happened to me regularly during the beta tests of OS3 but I've not seen it on my phone since the final release (strangely enough I have seen it in the simulator during development!).
Looks like the bug is still around though and will hopefully be fixed in a future release