R crashing after successfully running compiled code

I'm running R 2.15.1x64, though the same problem persists for 2.13.0x32 and
2.13.0x64.

I am trying to run compiled C code using the .C convention. The
code compiles without problems, dynamically loads within the R
workspace with no problems, and even runs and gives correct results with
no problems.

However, R will randomly crash within a few minutes of successfully using
the compiled function.

For example, if I run my compiled function using:
dyn.load("mycfun.dll")
answer<-.C("mycfun", parameters...), I get a completely sensible
result that gets stored to "answer".
However, if I try to do too many things to "answer", the R exits
without warning.
I've tried dyn.unload in hopes that R would become stable afterwards, but
in this case using the function crashes R without fail.

Usually, I can either plot, or view, or save "answer" to a file - but never
take more than a single action before R exits. This does not appear to
depend on how long R has been open. Initially, I thought it was a bug in
the "inline" function, but I'm finding the same problem now that I'm using
the dynamically loaded file directly. I'm used to R being insanely stable,
and am somewhat mystified by this whole problem.

My next move is to learn the ".Call" convention, as I suspect that
my problem is related to my "C" function using memory that R doesn't
know is used. But - before I invest a while lot more time on this, I'd
like to know whether anybody things this is likely to solve the problem.
If not, I may just want to run my code entirely in C, and forget the
R problem.

-- 
Adam Clark
University of Minnesota, EEB
100 Ecology Building
1987 Upper Buford Circle
St. Paul, MN 55108
(857)-544-6782

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