Really Slow Lan Speeds With Windows 7

I'm having exactly this problem too. I am the IT Manager at a large university campus and around a year ago I purchases two ReadyNAS 2100s for document storage. We're still in the process of migrating from Windows XP to Windows 7 on our desktops, and it's very noticeable that whilst documents on the NAS open very quickly in Windows XP, in Windows 7 there is a very, very significant delay - worse still when saving and closing. Users are constantly complaining to me. I've tried changing the MTU setting on the NAS, on a test Windows 7 client PC, with no improvement thus far. I've also ensured that Jumbo Frames are disabled (they're almost certainly not supported over our corporate network). I was going to disable journaling but from what I've read this would only give a modest performance improvement and is unlikely to be the root cause of this problem which seems to plague Windows 7 users in particular.