I just got a Konica Minolta Magicolor 4650 DN laser printer, and when I print on envelopes through the manual side feeder, the envelopes are printed on fast for the first 10-12 envelopes, then it slowes down to 10-12 second per envelope. Could this be a memory issue? And would it be printer memory or the computer spooler ? Can I increase it by setting, or do I need to insert new memory card? Any help is greatly appreciated.