I work actually not with IAR (M16c and Renesas compiler) but the procedure sould be same.
You need a timer for scheduling and time system (delay and so on). This timer has to work also without uCos (test this). Set up for this timer is to made after OSInit() in main. This timer calls OSTickISR() periodical. You need also a software irq for OSCtxSw().
Is it hung or not ? I dont have expertise in arm (board will be ready next week hopefully). Try to write independent procedure for uart handling and disable interrupts when byte is received then read OS vars content to find a cause . I also find playing with leds at some points in code very usefull when no JTAG . But you have one - did you try to trace it ?