problems with HP Photosmart C3100 series

I've had this problem for a long time but it's never stopped me printing:

I get this message "The application hpSuppliesTool quit unexpectedly. Mac OS X and other applications are not affected. Click Relaunch to launch the application again. Click Report to see more details or send a report to Apple."

This is pretty much anytime i try to do anything involving the printer. I just click Ignore and usually can carry on fine, clicking Relaunch just brings the message back up.

I've found that I can't access the supply levels for the printer, and today my printer started flashing at me - i've looked up what to do about this and followed the instructions to no avail.

I have this message in the print queue "Communication Failure: The computer is no longer able to communicate with your printer. Turn the printer off, check your printer connections and check for printer errors, and turn the printer back on"

The printer lights are telling me that there is no colour ink, however I only recently changed the cartridge so i know there is enough.

I think there may be another issue but i can't remember at the minute, i'll add a reply if i think of it...

Thanks!