IF header question

Investigation with a client lead to a little IF header problem. This is not
meant to be taken as criticism of the vendor, but would like people's
clarification. Scenario:

1) Client successfully "creates" a Lock Null Resource (LNR) by issuing a
LOCK request. The server result contains the lock token
"opaquelocktoken:xzy" in a Lock-Token header and in the XML.

2) Clients issues a PUT request after the LOCK above. However, the IF header
is sort of empty. Snippet of the request:

	PUT /Test/foo.txt HTTP/1.1
	If: ( )
	etc

As you can see, the IF header contains empty brackets. Our interpretation is
that the IF header if supplied MUST? contain 1 or more lists (as RFC2518 sec
9.4), which is why the client gets a 400 response.

What do people think?

PS Our email servers have been very busy last few days so apologies if any
of my posts appear to be a little out of sync.

Regards

Shaun Hall
Xerox Europe