What should my next move be concerning an editor?

I co-authored a book with a friend. We're first time authors & new to the publishing world. Another friend of mine works for Penguin Group and submitted the manuscript to an executive editor at Penguin. She told us the editor would contact us through phone or email. It's been four months and we haven't heard anything good or bad. We don't want to burn our bridges, but how much longer do we wait before we submit to other publishers? Do we send this editor a gracious letter & let her know that we hope she can look at our MS but we'll be submitting to other houses? Is there a certain protocol for this? We've been doing our research and I know that four months isn't long in the publishing world, but we could definitely use some advice on where to go from here.

Thanks in advance!

Ok, thanks for the good advice everyone, that's what I figured, I just needed the validation and some sanity....
- Jenn

Thanks everyone, I really appreciate your thoughts & experience. When my friend submitted for us she asked us for a synopsis & the full MS, we have the editor's name & everything. The only contact we've had with the editor is when my friend suggested we send her a thank you for accepting to read it...I know that still doesn't mean anything but because this is her colleague and we obviously appreciate that she did this, we took her advice...my friend said that if we didn't hear from the editor in four months (which we just hit) that she would ask her about it...anyone think this is a good idea or is this just going to annoy the editor?