I tried to use a usb plugin from an Epson Projector for my macbook pro 10.7 and I could not get the projector to show my screen.. I changed screen resolution as well - nothing (even rebooted)
Any ideas?

(first time I ever hooked up a projector to a macbook pro)

I have always used the thunderbolt port > mini display adapter > vga cable > projector. I thought the USB connection was to communicate the functions of the projector's remote control to the computer.

I always make sure everything is plugged in BEFORE turning my MacBook Pro. Epson directions use to say turn projector on first but a nephew of mine who is in the business pointed out that the computer can find the connection easier if things are plugged in first. No on occasion I have had to change the USB outlet that I had been using on the side of the MacBook.

Which Epson projector are you using?

And where does USB come in?
Doesn't one need to connect from the MacBook pro via the video ports?

I connect my MacBook pro to an Epson projector using the DVI port on the MacBook pro and the video input on the Epson.
No problem.

USB doesn't even enter the picture.

The projector model would sure help.

If it's one of the USB models, have you installed the supporting software from their site??

Probably you'll need their "USB Display v1.50" software installed at least.

Epson Support - Drivers, FAQs, Troubleshooting, Technical Support, Documents & Manuals for Epson Products - Epson America, Inc.

Maybe this will help:

Epson EX5200, FAQ - Technical Support - Epson America, Inc.

I didn't even know one could use USB to connect the video to a projector.
This support note of course assumes the specific Epson projector can accept video via USB - I have a USB port on my Epson projector but not for video.

I can just see it - jimwww is going to come back and say "I tried all that already"....

and this turns out to be another "Lion got cha"

And no mention of model etc.

At least the USB Display v1.50 software says it also works with 10.7. Yeah right!! So has some other software I have tried. So back to SL and most everything works.

One exception, a networked Laxmark Pinnacle Pro 901 using the recommended network setup for print and scan and finally gave up. yet it worked with 10.5.8 and 10.7.x. Wasted over 12-14 hours with three fourth level techs last late fall and even they finally gave up.

That's actually a pretty neat universal Epson USB solution for I'm assuming basic video projection and I didn't think that USB 2.0 had the horsepower or speed, but sure saves on having to buy or cart around all the other video type adapters etc. that were often needed.

Apparently it doesn't for video.

Epson MegaPlex MG-850HD Projector Review | Macworld