Hi Dingo,
I took your timer example and ran it using IAR6.10.5 and FSLMQX3.7 successfully on TWRK60N512.
Please ensure you are using IAR6.10.5 as IAR6.10.4 has compiler issues with FSLMQX3.7.
Hope this helps.
Regards,
David
PS
The release notes in the /doc folder let you know what version of tools work with current MQX version.