I just tested again (at home on my linux machine), this time I also use a namespace for my class:
it works fine, if I declare the variable with xyz::classname* variable and have a using namespace xyz; only in the header.
It also works fine, if I have the using namespace directive in header- and cpp-file, but declare the variable without explicitely used namespace
It does not work, if I only have using namespace in the header file, and declare the variable "normally" (without explicitely used namespace).
Or in short: cc always works if I have a using namespace directive in the cpp-file or declare the variable with xyz::classname* variable.
It does not work, if I only have using namespace xyz; inside the header-file.