>I inherited two VFP apps. There are two folders containing class libraries - I'll call them A and B.
>If I try to rebuild the project for A, it tells me that it can't find class library B.
>A should not be using B.
>I can't find where A is trying to use B. I used the code reference and and searched the classloc of the .VCX's but found nothing
>Any idea?

Try to run it from the command window, with on error suspend (unless it gets overridden in code, which you should temporarily comment out), see where it breaks.