In desperate need of printer help

I got an HP5550 printer a few weeks ago
The first thing I wanted to do was get the addresses printed.....so far I have not had any luck. Sometimes it prints sometimes not

The envelopes are 7 7/8 X 5 3/8 inches in size

That is not a standard HP size for printing, so I am trying to use the DL envelope size and eyeball it, which is working ok, but i can 't get any envelopes printed

I set the print properties to be DL envelope size, and somewhere along the way I shaged the orienataion so that the envelope is picked up width wise. I can't remember how I did this.

Can anyone please help???

Is there any way to clean out the printer queue? I know I can do this at work, but I don't know if I can do this at home

If it changed the way its printing then try changing it to either portrait or landscape (the opposite of wht it is now). That should be in the properties somewhere.
to clean the queue, you should be able to right click what you're printing (in the box that shows the status) and hit cancel printing.