I have a scheduler problem if i try to create and run a task in an external file.
I want to use the debug serial port for debug messages of my program.
Initialization works and outputs can be done but as long the Task Create and Task Function is in another file than the main routine it seems that the scheduler hangs up. If I copy task creation and task function code into main file it works as expected.

As basis I use the Demo Code for AT91SAM7X with GCC Compiler in eclipse with lwIP Stack.

There also seems to be a problem when I try to find out the problem with debugging. The init routine is in the external file and it works but I can't jump into it but for the delivered demo code the step into in other files work.

I think the kernel uses the system interrupt which is also used by the debug port. Try using the standard uart instead of the debug port, or move the tick interrupt to use a different timer. Some time back there was a thread that had a better solution in which the interrupts could be shared. You might find it with a search, but it was a long time ago.