Just to add something, if interleaving is turned on on your line, then your bras profile is likely to suffer, as it did with me, i had interleaving turned on and i was syncing at 8096, which meant my bras was 7000kbps instead of 7150kbps as it is now since interleaving is turned off, and i sync at full rate of 8128kbps, so they were robbing me of 150kbps and also they added roughly 20-40ms to my ping times, murder when playing games....
If you are getting just a few errors in your line and interleaving is turned on, I think its better to have the higher sync rate and have interleaving turned off and put up with a couple of errors than it is to have interleaving turned on for less than 100 errors aday.
Thats my opinion anyway, and i get the odd error with interleaving turned off, but it doesnt affect my connection at all, i loose about 30 seconds if that in error seconds aday, not much out of 24hours and my ping is good, so i am happy interleaving got turned off.