Hi Richard, It sounds like you are dealing with the dreaded X900 issues, this is a VERY frequent question and concern we get on the Forum, as well as experience ourselves here in the studio and R&D. Here's a blog post on our Inkjetmall site from Jon that explains why this is happening and your options for possible repair http://shopping.netsuite.com/s.nl/c.362672/it.I/id.266/.f
These are the instructions for flushing your printer with Piezoflush http://www.inkjetmall.com/tech/content.php?140-Flushing-Epson-Pro-and-desktop-model-printers-for-safe-long-term-storage-or-when-switching-inks
There has been MANY complaints on this topic, it is an epidemic to most owners of these printer models, you can find TONS of information out there pertaining to this complaint, we have found a very useful website called myx900.com, it is quit humorous and has a lot of valuable tips on repairing your printer.
Please let me know if you have any more questions, thanks-Kelly