Anyone ever had a problem with domain name propagation?

This might not be the right forum for this question and if it's not then moderators please feel free to move it.

I recently transfered a bunch of my websites from 1 HostGator account to another. I paid HostGator to do the transfer of the websites for me because I didn't have the time. After the transfer I updated my nameservers as normal. A few hours later, all of my sites were down except for my main domain. I thought it was wierd so I contacted HostGator and they told me it would take between 48-72 hours for everything to propagate over.

I was kind of irked because when I originally transfered hosting from GigaPros to HostGator all of my domains propagated immediately so I didn't think that a switch from one HostGator account to another one would work any differently.

Figuring there wasn't much I could do, I impatiently waited it out. Low and behold, the sites still haven't propagated. I bought a new domain name this morning, set up the nameservers, and it propagated instantly.

I don't get what's going on and have once again contacted HostGator to tell them that there is a problem, which they seem to have no idea why the sites aren't propagating. I've checked the nameservers for my domains at least 10 times each to make sure that they're pointing to the right place.

Has anyone ever experienced any similar problem?