[racket] Racket GUI error message

Hello everyone,

I wrote a library that defines and exports a function that creates sliders.
However, in another racket program, when I require both racket and my 
library I get this error message:

" cannot instantiate `racket/gui/base' a second time in the same process"

How can I solve this problem?

Regards,
José

-- 
José António Branquinho de Oliveira Lopes
58612 - MEIC-A
jose.lopes at ist.utl.pt