I downloaded the Maryland State tax form (PDF), filled it in and tried to print it to my HP LaserJet printer.

Nothing happens.

There is no error message. The printer's LED does not come on. There is no message logged to /var/log/cups/error_log or anywhere else that I can find. I can print other documents, including other PDF files.

Ultimately, I was able to print it by first printing it to a file and then using ghostscript with this command. (I only had to use sudo to write to the lp0 device.)

$ sudo gsc -sDEVICE=ljet3 -sOutputFile=/dev/lp0 mdtax.ps

Why can I print it directly with ghostscript but not via cups???

The information box on the top right says it all. It's intended that you fill in the blanks and print the form by pressing the large 'print this form' button, not download and print after the fact. Probably some PDF encoding.

Did that. Didn't work.

Since you obviously downloaded it, can you try to print it and see if it works for you? Of course, if it does work for you, that won't tell me why it wouldn't work for me, but at least I'll know it worked for someone.

Failed for me too. My printer spit out two empty pages and called the job complete. I got this from my cups error_log.
No error, but also no print.

Tried this under Suse 9.3 Pro, on an old HP Deskjet 882c. Like you, I have no problems printing other PDFs. Notice in the quote above that the filters in sequence are: pdftops, pstops, foomatic-rip. So, the failure is somewhere else.