Note sure what the trouble is, but there are a number of things you could try. These are mostly all purpose troubleshooting steps.
First, make sure you're installed all software updates, of course, for the OS and iTunes.
* Delete "Podcasts" folder from ~/iTunes/iTunes Music. It may just be a corrupt podcast.
* Also, try disconnecting from the internet. Maybe there's something with one of the podcast feeds.
* You could also launch into a new iTunes library to see if the podcast problem is with your install of iTunes or just the library. Launch while holding "option" and iTunes will prompt you to choose a new library or create a new one. (This allows you to have a couple of different iTunes libraries, btw-- for instance, one might live on an external hard drive.)
or
* Delete iTunes preference plist (com.apple.iTunes.plist which is in ~/Library/Preferences)
or
* Backup both your iTunes library data file and the xml file (~/iTunes/iTunes Library is the data file; ~/iTunes/iTunes Music Library.xml is the other). Then delete the data file. When you launch iTunes, it will rebuild a data library file from the xml file. This is a way to fix a problem with a corrupt data file, but it may-- I don't remember-- make you lose user-specific metadata. In any event, you made backups so just restore from them. This is kind of a nuclear option, just short of trashing everything and starting a new library.