How to detach binary objects/libraries?

Hi all,

First, I want to apologize if this question has been already answered. I
have a RedHat 7.2. system with recently patched version of R-1.4.1. I'm
in a process of writing R package, say X, that loads some C++ code.
Currently, while adding functionality to it in both R and C++ sources,
I'm getting crashes every time I detach/load/access the C++ function(s).
Typical transcript follows:

library(X)

Loading required package: mva

is.loaded("exp_dist_fast") # The name of the C stub function

[1] TRUE

detach(package:X)
is.loaded("exp_dist_fast")

[1] TRUE # Problem?

library(X) # Load X after changes in the C/C++ code
is.loaded("exp_dist_fast") # or .C("exp_dist_fast",...)

Process R:1 segmentation fault at Mon Mar 25 12:17:57 2002

What is the way to cleanly unload the object code and is there better
mechanism than detach(package:X)?