I have an HP 4050N and have the same sort of problem.
I would like it to print an envelope and then the letter, or vice versa, but if there is an envelope in the front tray, it wants to print the letter onto the envelope.
The annoying thing is that from the PC that is also on the same network, it does what I want it to do.

Seems not all drivers are created equal.

If anyone does have a fix, I too, would be interested

P