Since you're doing multiple machines, you're having trouble w/pushing an image out. Since it works w/just a few machines but not w/a bunch I'd normally say it's just a network scaling problem. But if the same exact hardware (down to the switch, cabling, etc) is all working under 8.2 but not under 11, then I guess it can't be the hardware.
In that case, the next thing I'd try is checking the driver. Are you booting all your v11 clients using a boot floppy/cd/PXE that was built using the Ghost Boot Wizard built-in to v11? If so, locate the driver you used back in v8.2 and integrate that into the GBW for v11 and then recreate the boot-disk. Or better yet, just get the latest greatest DOS drivers for your NIC from your vendor and/or manufacturer (eg: Dell might be the vendor but the board and NIC was still mostly manufactured by Intel, and Intel might have good drivers that Dell doesn't.)
If using your known-to-be-good drivers from v8 or the newest-drivers-from-vendor both don't work, the next thing I'd try is to isolate which client(s) causing the problem. It'll take time. But do six batches of four systems each. Chances are, you'll notice one (or more!) batches will fail, or underperform. Once you've isolated it down to a batch of four, split that into two groups of two systems and try again. Hopefully, you only have one "oddball" machine that's just slowing the entire group down. Once you've found that oddball machine, recast to 23 of the 24 machines, leaving out that one oddball machine (or two oddballs or however many you've found.) If you have such an oddball machine, look at it carefully. Is the hard-drive on this one a Primary Slave instead of a Primary Master like all the others? Is the BIOS revision the same as the others? Are the BIOS settings *identical* to the others (the wierdest BIOS setting can affect Ghost - USB crap caused me a lot of problems even though I have no USB devices at all!) There may be some "weird thing" (a technical term!) about this one machine that didn't affect v8 but does affect v11. I can't imagine what it would be - despite all the version increases, the core client itself hasn't gotten all that massively more intelligent or complicated (although code-writer of client would probably disagree!)
All in all, I'd bet it's the driver in v11 that's screwing up and the driver you used in v8 was good.
Good luck,
PH