Irregular/Slow Read Speed from NV+ over Gigabit

I'm struggling to understand my problem, but i'll do my best to explain below.

Basically: i get wildly different results when copying files/folders in OS X Finder from my NV+.

Ok, getting the specs out of the way:

Netgear ReadyNAS NV+
4.1.7 [1.00a043]
X-RAID
Seagate ST31500341AS 1.5TB x4
User Security Mode
Netgear ProSafe GS108*

MacBook Pro, mid-2007, 2.2GHz C2D, 4GB RAM
FUJITSU MHW2120BH 120GB 5400rpm
Toshiba MK1059GSM 1TB 5400rmp via external FireWire 800
Gigabit wired connection, Automatic settings**

OS X 10.5.8, Finder
protocol: AFP, SMB, NFS***
Monitoring network speeds in Activity Monitor's Network tab

So i was doing simple drag-and-drop copies of fairly large video files from my ReadyNAS onto a FireWire 800 drive. The files are anywhere from 500MB up to 6GB, the majority being around 1GB, some grouped into folders. I had 1TB i was trying to fill up on a deadline and was frustrated to find out it was taking way longer than it should.

Now, occasionally a file would copy as fast as i'd expect, going 30–50MB/s, taking maybe 30 seconds. When i started trying to copy multiple folders i noticed a problem. Those transfers would only go 1–10 MB/s — way too slow for a gigabit connection. The large 6GB files seemed to always go at higher speeds (30–50MB/s) when copied alone. However, like the title says, it's all irregular — some single files would go slow as well, but folders and multiple files would never go at expected gigabit speed. I tried different files from different locations, different sizes, different combinations. Occasionally i'd get 30MB/s and on the next file i'd try it would drop to below 5MB/s. Most of the time is was around 5MB/s.

I was hoping to select all the files and folders and drag them over for a one-time copy, but with the slow speeds it was going to take more time than i had. And as i said, copying files one-by-one did not guarantee top speed either, besides i didn't have time to babysit it and copy hundreds of files individually.

Obviously, because some of the files would sometimes read at the expected speed, i assume everything with the "environment" (all the hardware and settings) is set up properly. So i'm tending to believe there's something very odd going with the NV+ reading files. Or maybe an issue in Finder when copying multiple files or folders containing multiple files or subfolders. I say this mainly because most everything else tested out to be a non-factor, though there could easily be something that i'm missing.

I tested the write speed of the target drive, and it's 70MB/s — probably capped by the FireWire 800 connection. So that's not the problem. The system drive inside my MacBook Pro writes about 30MB/s. I tested copying to it as well and got the same irregular results — usually under 10MB/s. I'm also fairly sure the network connection is legit because when i would try to copy the same file a second time, the network speed would spike up to about 70MB/s at first then drop down under 10MB/s — because it was cached in memory on the NV+ then started reading from disk.

And of course i tried all the options and tricks i could dig up on the forums here (though most of them affect writing to the ReadyNAS not reading from), and none had any noticeable effect either way.
* with/without switch (direct connection to NV+)
- jumbo frames on and off (both on the NV+ and my Mac at 1492,1500,7936,9000)
- journaling on and off
- disabling extra protocols, services, and addons
** automatic and manual IP and ethernet settings on my Mac
- tcp.delayed_ack 0/3
*** AFP, SMB/CIFS, NFS protocols

Unfortunately i don't have a Windows machine with a Gig port to test.

This sounds a lot like the unresolved problems many others have reported with slow speeds so i apologize if it's a repeat. Please chime in if you have any ideas, comments, questions, or new things i can try.

Thanks.