I have a Sony DCR-TRV30 NTSC MiniDV. Transfering from the camcorder to the PC works quite well. After creating a movie, uploading back to the camcorder is choppy. There are blue screen sections in between video sectubs. I am using a 1394 connection between the two units. This occurs with another computer too.
I haven't experienced the exact problem you mention, although I have found transfer from PC to camcorder to be a rather hairy business. For me, it often fails altogether, although that could be because my PC is a bit old...
I could imagine that both "choppiness" and temporary blue screen artifacts could be caused if your computer is unable to provide video frames at the requisite rate. The camcorder is obliged to continue recording, even if no signal comes, and if there is no signal, the playback will be blue as you no doubt are aware. What speed are the PCs you have tried this with? And are you sure the HDD drives are DMA-enabled? Plus, you had better also confirm you are trying to transfer from HDD to camcorder, NOT from a DVD. That would be much harder for most PCs.
This is probably a really dumb question, but you are using native .avi files, rather than a rendered mpg movie, I hope! (I can't see how it would work at all if you were trying to transfer something that wasn't .avi)
Now assuming that your system is "on the edge" of being able to transfer video back to the camcorder, I'll suggest the following:
1) try transferring a very short clip to see if that can get back to the camera perfectly. If yes, try gradually increasing the clip duration until you find the breaking point. That may tell you something interesting.
2) make sure you have closed EVERY unnecessary application running on your computer. With my current set-up, I have to close everything, including System Tray apps, before I can capture video without dropping frames. Plus, I had to DISABLE the W2000 indexing process ("findfast.exe") altogether, otherwise I just crashed after 25 seconds.
If both the PCs you have tried are approx 1.4 GHz or above, and you are reading .avi files off the HDD, not a DVD, then I'll be pointing the finger at your camcorder.
Well, not sure I've given you a solution here, but perhaps some food for thought.