Unfortunately, some early versions of Motif had bugs in this area, so be careful, especially with Motif 1.1. Better yet, upgrade to Motif 1.2 or Motif 2.0. As you probably know, there are now several high quality memory debugging tools on the market. While good programming technique is always important, these tools will usually catch the things you miss. I highly recommend using them.
Many widgets provide convenience functions for setting and getting resource values.
Also, the convenience functions tend to be better documented than the resource values. Debugging Now that we've learned to code defensively, hopefully we won't have any more resource syntax errors. In the remote case that you do find get one, however, here are a couple of hints for debugging them. It can be very helpful in finding incorrect resource settings. Finally, you could use a source level debugger to examine internal structure of widgets.