Passing string to facebook api for wall post, ignores newline

I'm using the Prime31 social networking plugin, but that shouldn't be having an effect on this.

I've tried:

 \n
 \r 
 system.environment.newline
 <br>

and in every case the tags disappear and the string is unaffected.
The image I'm linking to appears without a problem but the caption I'm passing
remains on a single line unless word-wrapping comes into effect.

Anyone run into this before/know how to fix it?

Thanks in advance, I appreciate it.