Acrobat 9 Reader and HP DesignJet 500

I have a client who uses the above printer, with 42" rolls. Everytime they try to print a PDF via Acrobat Reader, a huge, arc shape area of the print is missing.

It only does this when printing from Acrobat Reader. I have updated their drivers and firmware but still the same. There is 1 entry at HP regarding this which goes back to older versions of Acrobat ie pre V6.

No matter what the settings are, the result is most of the print is missing. However, printing onto normal size paper results in a perfect print, A4 etc.

Any help would be greatly appreciated.

Thanks in advance. Windows Vista Business 32bit

Adam