problem using compare revisions

Hello,
 
I got the following problem with my system:
 
Server: WinXP + Apache 2.0.54 + Subversion 1.2.1
 
Client: TortoiseSVN 1.2.5

When I choose a versioned text-file, run "Show log", click on two revisions and select "Compare revisions" I get the following error:

    Failed to fetch lock information: 404 Not found ( http://intranet)

It works, when I choose "Show differences as unified diff".

It also works, when I use a local repository and not the http-access.

It also works, when I choose two revisions of a folder and double-click on one file.

Is there a problem with my server or with TortoiseSVN?

Jan

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