uhm who knows, I've been synchronising music via Mediamonkey from a very long time and everything has always gone right
beside this "unkown error", itunes doesn't even seems to automatically find new updates for my apps but I need to click on verify button
I might be wrong (it happens often eheh), to me the assassin is iTunes (ok I admit it I hate iTunes since the very first day)

ps
at the moment the mediamonkey version on my pc is 4.0.0.1381; I'm going to check for updates.

latest mediamonkey, same error.... :\ hopefully this is going to be fixed in iTunes 10.5 .....

I have lived with error 1660 for a long time and went to another forum and found the solution today. In my case I just had to allow iTunes through Windows firewall. Here are the full instructions - I did NOT have to disable my anti-virus.

From another forum

I disabled my antivirus.
Tested iTunes and the error got fixed.
I checked Windows firewall and iTunes was disabled for some reason.
I enabled iTunes through Windows firewall and all is well. (THIS IS ALL I DID)
I also made sure to reactivate my antivirus after fixing the error.
I tested one more time and everything working fine.

I get this error when i have recoverygaurd installed to prevent my iphone updating to latest firmware as soon as i uninstall recoverygaurd in cydia error goes away

Originally Posted by DunderMifflin

I just updated iTunes to version 10.4.10 from the version just prior to that and now, each time I sync, I receive a message at the end saying an unknown error occurred (1660).
The sync seems to be complete and just to make sure I run a backup and I don't get the message just running the backup. I turned off the firewall and shutdown my anti virus program but I still get the message.
Anyone have any ideas why I get the message and how to cure it.

iPhone 3G
IOS 4.2.1
Jailbroken running ultrasn0w

Recoveryguard is easily bypassed by putting the phone into DFU mode and restoring that way. If you are jailbroken, you should avoid "upgrading" and instead restore/set up phone as new. Upgrading drags with it a lot of unecessary junk unless after the update you reinstall ALL the same cydia apps you had installed prior to the update.

Bingo! Recoveryguard is the troublemaker

Originally Posted by baro

Bingo! Recoveryguard is the troublemaker

That's the point of recoveryguard (to prevent accidental updates). It's easily uninstallable (or bypassed by forcing recovery or DFU mode prior to restore)

It was fixed this problem?

Is never nice when a post it doesn't show if the problem was fixed or not.

Uninstalling recoveryguard fixed the problem, sorry if it wasn't unclear