R help - Dec 2006 - Unable to build a package

Hi everybody,

I've recently write my first R package and when I run :
    R CMD check myPackage

I got the following message :
* Installing *source* package 'myPackage' ...
** R
** save image
Error in exists(x, envir, mode, inherits) :
    invalid first argument
Error: unable to load R code in package 'myPackage'
Execution halted
ERROR: execution of package source for 'myPackage' failed
** Removing '/home/dmahieux/svn/microarray/src/package.Rcheck/myPackage'

In this package, I've 2 classes :
 - a virtual one : MArrayExperiment
 - a second which extend the first one : AffyExperiment.

I think that the problem is when building AffyExperiment , the 
MArrayExperiment is not yet known and so the exists function is aborded.

Is there a special trick to tell that the MArrayExperiment class is 
present in my package ?

Sincerely...