A similar thing is happening to me, although I'm not listening to the radio. Whenever I try to add tracks to a playlist from the main streaming part of Spotify, the program freezes and I have to use Ctrl-Alt-Del to get out of it.
OS: Windows XP Home Edition - Service Pack 3
What and how: Several different tracks. I tried adding them by right clicking on them and selecting Add to, then choosing a playlist.
I am really getting pi**** about Spotify for Windows... Every release since the 0.8.5. one is as worst as the release before. The program keeps crashing, it is slow as hell and nobody at Spotify seems to do something about it.
In the last days Spotify keeps crashing down when I remove played songs from a playlist while there is a song playing in that playlist. That's not normal and I never had that problem before! The whole program is slow, needs a minute to fully load so that I can search for something or play a song without crashing.
But hey, I know I am just a sheep which is paying a big company for a working program. But they probably just sit at their big desks at keep laughing at us dumb users who pay and pay and pay and they do nothing to fix the problems.
There is a really easy solution: go back to release 0.8.5. --> it worked and after that release it just gets worse and worse!!!