Naturally, the first response from Digital is that it is likely to be a NetApp problem, and the first response from NetApp is that it is likely to be a Digital Unix problem. Any suggestions on how to determine where the problem lies?
What software release is the NetApp box running?
Bug 4604, "NFS v3 layer ignores readdirplus dircount parameter", has caused problems with DU 4.0 clients; the fix is in 5.0, so if you were running a pre-5.0 release, that might be the cause of this problem.