I'm exporting a project that's huge, in wav format, it's sitting at 880Mb, then I try exporting it to wma format, hoping it's gonna be compressed down to around 50 Mb to put on a CD-R, and all I'm getting is the message about codecs.............. completely baffled, thanks

computer specs?  OS version?  Exporting out of Sonar or a different method?
 
What is your method that is resulting in the error?  step by step.
 
Have you tired converting on a smaller chunk or a different file?  Have you tried it on a different machine?
 
You really have not provide enough information to assess and provide any kind of support for your situation.
 
Export WAV use Sound Forge for the codec you want.  that's my answer.
 
 

Not meaning to be demeaning, but I can't remember the last time I used a CD-R