I have been at frustrated by failed builds on my package on R-forge. It seems that the problem is a failed build of RcppArmadillo itself on 13 July.
The culprit seems to be an unterminated #ifndef in Module_generated_CppFunction.h:22:0
I don't know why but the R-forge folks let the offending source be the library I was calling from my own #include RcppArmadillo.