If you mean you want to reset all the card statistics for a database,
you could use Mnemosyne to export the database and select "Reset
learning data on export" and import it back as a .mem file and then
transfer to iSRS.
If you mean resetting just the repetitions count, currently there's no
way to do that. iSRS was written as a companion tool to Mnemosyne 1.2
to allow you to study the same .mem database on your iDevice and then
transfer back to your PC, so it is assumed you want to preserve all
your stats.
A few users have reported issues with iSRS Sync and crashes -- for now
I recommend manually copying .mem files to and from iSRS with the
iTunes File Sharing (
http://support.apple.com/kb/HT4094) feature until
the next version is released. The next version contains many changes
under the hood and will address the synchronization issues. I can't
give an exact ETA, but hopefully in the very near future :).
Best Regards,
iSRS Support