Transcoding would imply that it's not even gotten to the bit where it actually transfers the sound file to your iPhone yet. iBrickr is still trying to convert your file from one format to another. It sounds like your source file isn't one that FFMPEG likes, even though it should "theoretically" accept every type of format.
If you can, re-encode your original file and then try running it through ibrickr again. Alternately, you can restart your computer to try again, and if that doesn't work, you may want to install some codecs to handle your audio decoding/encoding:
FFDShow is a very good codec, I've not had any problems with it and it complements AVSynth and VirtualDub very well. The only thing you may want to do is edit it's configuration to not show the tray icon every time its decoding something, it's kind of annoying, heh.