We are having similar problems and try to track them down for the last few
days. I set up a MS Virtual Machine running only Office 2003 SP2 (german) on
a Windows Server 2003 SP1. Latest Windows & Office Updates are applied. In
the VM I work as "Administrator". Therefore registry access (as you wrote in
the previous post) shoudn't be an issue.
I then "played" around with different real and implicit document checkouts
("checkout" / "edit in MS Word" function by using dropdown). I opened
documents alternating from "both sides", meaning from my PCs IE and from the
IE running insied Virtual PC.
I configured IE to not use any http proxy (which we normally do because I
figured that OPTIONS or WebDAV requests might be filtered by our Reverse
Proxy [methods described in http://support.microsoft.com/kb/838028/en-us])
Funniest things are happening: Sometimes I could open Documents from one
side (so either from normal Client IE or from VM IE) writable, but only "read
only" from the other although using the same user credentials. Worst thing I
experienced (also seen on Google groups): checked out a document using the
drop down menu function, opened the doc "from the other side" using the same
or different user credentials: read only as expeced. Then opened the document
using "edit with .." on the first side and getting: this document is checked
out by <my own login>. Doc is then opened read only!!
I could not find any real logical relationship so far; I'd just call it a bug!