r800 pring in wierd order

ok a couple of questions really running vista and printer epson r800 works
fine all drivers are up to date, mosty of the time it is behaving but
sometime the printer is doing this on occasion..

1. printing the document/ picture then feeding 3-4 more blank sheets through

2. printing the first few lines of document/picture running paper through
then printing the rest on another piece of paper.

just wondered if there is anything that has been pressed ie collating etc
that is causing this or should i reinstall? just somem advice would be great
thanks kelly