While the problem clearly is with the proxy, which should serve temporary redirects only, there is still the question how to recover from this. Since Liferea 1.1.4 your original subscription URLs are stored in the feed cache, so that it can be used to recover the now invalid URLs.
There is no way to do this in the GUI though, I just see no simple way to provide a GUI based restoration interface. As an alternative I advise you to use this script. After downloading it, terminate Liferea and run it as follows:
$ sh recoverFromProxyHell.sh > feedlist.opml
After successful execution (depending on the number of your feeds this can take some time) please check the contents of the created file before copying it to ~/.liferea_1.2/feedlist.opml and backup the old feedlist.opml as necessary.
For completeness: If you value your feed list back it up regularily!