Slow share performance on my RN 104 since upgrading to 6.4.0

I don't personally think that this is much to do with Antivirus (at least for me).

I never had AV switched on, and saw my performance drop by half when 6.4.0 was installed.  I also got the crashes that others got, but those seem to have abated since 6.4.2 and I've not had one (though I am hesitatnt to say they have gone away completely, as originally when I got 6.4.0 I didn't seem to get system lockups - that took a while to start happening).

Here's what I'm seeing from my RN104.  I'm running the NAS tester from a RAM disc so as to rule out my PC's internal RAID being any sort of problem.

NAS performance tester 1.7 http://www.808.dk/?nastester
Running warmup...
Running a 400MB file write on V: 5 times...
Iteration 1:     28.79 MB/sec
Iteration 2:     29.09 MB/sec
Iteration 3:     28.65 MB/sec
Iteration 4:     29.13 MB/sec
Iteration 5:     27.33 MB/sec
-----------------------------
Average (W):     28.60 MB/sec
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Running a 400MB file read on V: 5 times...
Iteration 1:     37.81 MB/sec
Iteration 2:     38.16 MB/sec
Iteration 3:     38.43 MB/sec
Iteration 4:     37.20 MB/sec
Iteration 5:     36.68 MB/sec
-----------------------------
Average (R):     37.66 MB/sec
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As mentioned before, this 25-30MBps performance is half of what I was seeing under 6.2.5.