I had a similar issue and solved it with Google's support advice. In my case, there were two printers with the same name and that caused a problem. Also, you do not note what OS you are using, but there is a requirement for Windows XP to have sp 3. I am also using Google Chrome as suggested by Google.
Make sure your Google Cloud Print connector is running on a computer
that is turned on and using the latest version of Google Chrome.
Make sure your printer is on and connected to the computer running the
Google Cloud Print connector.
Make sure you're printing to the correct printer. Sometimes, there may be duplicate printers shown.
In Google Chrome, select Settings and click the Show advanced settings
link. In the "Google Cloud Print" section, click Sign out of Google
Cloud Print. Visit the Google Cloud Print management page and click on
Printers. Delete any duplicate printers (printers with the exact same
name) and then sign in to Google Cloud Print again.