On my Mac (OS X 10.6.7) using iTunes (10.2.2 (12)), if I drag a bunch of files into my app via iTunes' File Sharing, the first dozen to four dozen files transfer quickly ... then, sporadically, about one in five files hangs for a minute or two.
I'm dragging 209 files, with a total of about 35 MB (so, each file averages about 170 KB).
The hangs seem to occur more often on the "loaded" iPad (4.3.3, cellular/ATT, about 280 apps), and (IIRC) never on the unloaded iPad (which was on 3.2 until last week, and is now on 4.3.3).
Xcode is not active.
The app is NOT "active" (foreground or background) on the iPad. (Indeed, no apps are active.)
When the hangs occur, the Mac's CPU usage does not increase...stays near zero.
After the last file allegedly transfers, iTunes sometimes beachballs for several minutes. (Twice, I've had to hard reset the iPad.)
I've tried dragging several dozen files at a time, but still see sporadic hangs after the first dozen to four dozen.
The files are binary files that have a suffix not otherwise recognized by any app other than ours (I.e., they're not named with a suffix like ".zip", in case there's any chance that iOS would be opening them and scanning them :)