So the problem occurs when a user logs into a machine before OD communications is completed? Like after startup? Does it happen with 10.7.5?
You might try the solution from http://support.apple.com/kb/TS3556. However, since that script only works in 10.6, replace it with this dumber script:
#!/usr/bin/ruby sleep 60 exec '/Library/Filesystems/Xsan/bin/xsand', *ARGV
This simply causes Xsan startup to be delayed by 60 seconds. If the problem is that OD hasn't finished binding to network directories before the Xsan volume mounts, this might work around the problem. You may need to increase/decrease the sleep time.
Does this help?