[R] error related to approxfun in R 2.7.0

[Karl Marx]

I'm testing R version 2.7.0 on windows and there seems to be a
compatibility issue with objects that were created by "approxfun" in
older versions. As long as the objects were created in version 2.7.0
things work ok, but calling the interpolated functions from R version
2.0.1 causes this error:

Error in .C("R_approx", as.double(x), as.double(y), as.integer(n),
xout = as.double(v),  :
  C symbol name "R_approx" not in DLL for package "base"

What's the problem and how can t be resolved (need to be compatible
with old data)?

Regards,
K