Please help!

We have an '06 Dodge Durango that has ran great for us since we bought it brand new in Feb '07. Haven't had any issues with it at all.

Today I went to start it to go to the grocery store and it turned over fine but then let out a high pitched squel (I automatically thought it was the belts and it would stop after running for a minute or two since it has been so cold here in MN this last week). Well I went out about 5 minutes later to leave and it wasn't running. The regular lights were on on the dash like it was running fine but the engine wasn't running. No check engine light, nothing. So I turned it off, turned it back on a minute later and it did the same thing: turned over fine, high pitched squel then putted out. Well I opened up the hood and turned it on again... noticed the squel is coming from UNDER the truck, like near the middle section (by the driver's door maybe?). When I turned it off (it was putting anyway so I just shut it off), the squeling continued for maybe 30 seconds and sounded like a helium balloon letting out air.

Anyone have any idea what this could be?

Thanks in advance!