assertion failed: lower_constant (Internal Compiler Error?)

Hi,

I am getting the following error:
error : assertion failed: lower_constant: bad kind (shared/cfe/edgcpfe/lower_il.c, line 5639)

From previous threads, I assume this is an internal compiler error. The line in question is a copy constructor:
_MatrixData(_MatrixData<type_numeric,3,1> const& other) : data(other.data) {}

This should be valid C++ code (modulo possibly the underscore+capital). It would be very difficult to try to pull out a minimal example. If you really need it, can you at least tell me what to look for?

Thanks,
Ian