That might be because like virtually all printers, the P2055d is embarrassingly poor in terms of RAM. A single page at 1200x1200 DPI is around 18MB. So... it may very well be that a full page at 1200x1200 DPI, plus the actual document, plus some fonts is a challenge for the printer's meager 96MB of RAM. There are no RAM issues whatsoever at 600x600, so...
Personally, I'm using FastRes1200 because it looks excellent and is fast. Plus, there's no weird cheating around with high DPIs and low LPIs. Good quality, reliable, reproducable, and fast. What else do you want.