From http://bugs.debian.org/524108:

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Since upgrading to OpenOffice.org 3.0, documents opened from an AFS 
filesystem open read-only. I have full write access to the filesystem, and
changing the locking option in soffice.sh makes no difference.
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I asked him whether it still applies to 3.1 and it does.

An other person found the reason and the workaround:

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e get this for all document formats where user opening the file does 
not have regular unix perms to write the file.

This looks like openoffice 3 trying to be smart figuring that if file 
perms are 644 and you're not the owner you won't be able to write to the 
file ... that's correct except for filesystems like afs that have their 
own acl system and completely ignore the regular unix perms.

So it looks like an upstream screw up in the oo.org 3 cycle.

As a workaround you can chmod all openoffice files to 666 and folders to 
777 and let afs handle read/write access when it has to.
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(I'd think that this then also would be the case for other ACLs, like
the ext3 ones)