hummm, looking for the potential easy - to solve problem (as I know nothing about the software bit
)
Does it happen on copies (or, if that is possible: if you print an "internal page", ie a configuration report)?
Does it happen for different document types? (Ie does both a PDF and a TXT file blur?)
Does it happen for one or more colours? (Drumtest is useful for checking that, but mostly if it is deletions, so there is no guarantee the blur will be noticable)
http://dc.communityprinters.com/color/ColorDrumTest%2013x19.pdf
(if green goes blue Yellow drum is the problem and vica versa if it goes yellow)
if there are marks at specific intervals that might also be an indicator