Hi. This error means "A carriage jam has occurred".
The steps to correct this problem are (from HP support):
Step one: Move the carriage
1.Lift the top cover of the product.
2.Turn the product off, and then turn it on.
3.Unplug the power cord from the back of the product when the grinding noise starts.
4.Move the carriage towards the middle of the product (this procedure may take a couple of tries to get the timing correct).
Step two: Remove the cartridges
1.Press down lightly on top of the cartridge latch.
2.Pull out the bottom of the latch to unhook it.
3.Slide the print cartridge out of the carriage.
4.Repeat the steps for the other cartridge.
5.Close the top cover.
6.Reconnect the power cord.
Step three: Reinstall the print cartridges
1.Open the printer cover.
2.Wait until the carriage moves to the right side of the printer and is idle and silent.
3.Press down lightly on top of the cartridge latch.
4.Pull out the bottom of the latch to unhook it.
5.Hold the print cartridge so that the copper strips are on the bottom and facing toward the printer, and then slide the print cartridge into the carriage.
* Install the tri-color print cartridge in the left side of the carriage.
* Install the black, photo print cartridge, or the gray photo print cartridge in the right side of the carriage.
NOTE: To easily identify the correct side of the carriage in which to install the print cartridge, match the symbol on the print cartridge label with the symbol above the carriage.
6.Push down on the print cartridge latch until it snaps closed.
7.Lower the cover of the product.
For other errors indicated by the lights flashing follow the link:http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00575972&lc=en&dlc=en&cc=us&product=467980&lang=en
Hope it helps, if it helped you, please rate the answer. For further assistance please reply back.