Very interesting. This may be the answer to the file number limit.
All of the tests below use the same iTunes database using stock ipod firmware. The ipod logic boards are known to work fine with Toshiba 240gb HD. All are 64k RAM.
Update for 240g Toshiba HD V7:
I have loaded 51922 songs on to the HD ipod and have used it for a week. No issues.
Update on BP4 mSata V5.5:
I've loaded 29767 songs without heat or 0-song issue.
Update on 256g SD Lexar+Tarkan V7:
I managed to load about 16k songs before the ipod locked up my computer. What is interesting to me is that the number of songs at failure is so variable and inconsistent., and have ranged from 12k to more than 20k. Ipod loads about 1000 songs, and then reports an error 69. If sync is selected again, it loads normally until it repoerts another 69 error. This error is reported on random songs, and does not report for other ipods.