I am having the same problem and its now Feb 2012. Its crazy, i can open up a podcast project i did on another computer running leopard , bounce it on my macbook pro 2.4ghz running snow leopard and its fine and the URL links are included. However, if i try and create a new podcast project or even update an older working project ( that previously worked the URL links disappear.
I am at my wits end, any help would be appreciated. I have tried shuffling the parts along a touch etc etc etc.
APPLE PLEASE HELP???
After "burning my brain" with this issue I solved it, at least on my case.
I was trying to export an long enhanced Podcast (1h 17mins) with chapters, artworks, URL links on artworks, etc.
While on the Podcast preview everything was ok, artwork and URL were showing, URL links were working, when I exported it to Disk, the links would not show. Everything else, artwork, chapters, was working. But NOT the URL links on the chapters/artworks.
Its as simple as this: the Podcast size Bar limit is 1999. When you start the Podcast, the menu asks the BPM you want to set the Podcast to. If its a big Podcast (like mine was), you have to lower the BPM, so the Bar length NEVER EXCEEDS 1999. You have to this in the BEGGING of doing the Podcast, as you can't change it later.
To check the Bar size just change Garageband "display" (next to the Transport controls) from "Time" to "Measures" and check the Grid on top of the Arrangement. Its now showing "Bars".
After lowering my Podcast BPMs (to 80 BPM) I was able to fit the 1h 18mins on 1537 Bars, and when I exported it, ALL links were working ! So check your Podcast Bar size, that might be the problem...
Im using Garageband '11 (6.0.5) on OSX 10.7.5
Hope I helped !