Happens to me too. iTunes just does not advance past a certain item while syncing, the progress bar just stops, and apparently no more songs are transferred.
Left it on over night, but the progess bar remained stuck. iTunes remains as responsive as iTunes under Windows can be. 😉 Clicking the x in the info pane appears to properly stop the sync.
First time iTunes got stuck at song 2/141 in Step 2/3.
I tweaked the bitrate setting on the sync panel to force a re-sync of most of my songs, and it got stuck on song 2/1858 - but that's another song entirely, not the same as the one from before.
Restoring the iPod to factory defaults did not help. Got stuck on song 2/... again.
This bug appears to be unaffected by the "Enable Disk Use" option, as it occurs regardless.
It appears that item number one seems to sync just fine, iTunes just never manages to get item number two to transfer. I have played around with the settings, apparently the files itself are of no consequence, but rather its position in the transfer queue.
Ticking/unticking the "offending" songs did not help, sync always appears to get stuck on song number 2 in the queue.
iPod: 6th Generation nano 16GB
OS: Win7 Home Pro 64Bit, 16GB RAM, >>10GB free space on all drives.
Data to sync: Mix between MP3 imports, ALAC CDrips and iTunes purchases
iTunes sync settings: sync only ticked songs, Convert higher bit rate songs to 192kbps AAC