I had sent out a package on 10/3 (label created with Click'N'Ship) and it never did show up in the system, not even the usual message you get after creating a label but it hasn't been scanned yet. Even asked about it at the service counter, and they were clueless. Today I received this email and I'm passing it along in case anyone else might have been affected.

USPS said:Due to a technical issue, you may have experienced difficulty receiving Track & Confirm data for Click-N-Ship domestic Priority Mail labels printed between Thursday, October 1st, 2009 and Tuesday, October 20th, 2009.

If you generated a domestic Priority Mail label on Click-N-Ship within the indicated timeframe and have had difficulty with obtaining Track & Confirm data from USPS.com, we apologize for the inconvenience. If you would still like to obtain Track & Confirm data for a domestic Priority Mail label printed between the dates indicated above, please follow the instructions below:

In the Track & Confirm field on usps.com, please add two (2) additional digits, "94", to the left most position of the twenty (20) digit tracking/label number. For example, if the tracking/label # is 0550 1699 3200 0006 9161, the tracking/label # necessary to receive tracking data would be 940550 1699 3200 0006 9161.

Additionally, your domestic Priority Mail tracking number(s) for labels printed within the date range above will be automatically corrected Thursday, October 22nd, 2009, and available in your Shipping History. Please feel free to visit www.usps.com/clicknship.

Once again, we apologize for any inconvenience this may have caused, and we sincerely appreciate your business.

Thank you,

USPS Click-N-Ship Team

Dupe.
See: http://www.fatwallet.com/forums/online-auction-info/958950?

USPS notification on these issues is WAAY late.