As documented with the product, Scala Designer supports the “Open QuickTime v.3.0” format or earlier only. QuickTime 4, 5 or 6 files and files that are encoded with proprietary CODEC’s–e.g. Sorensen, can not be used.
Starting with Scala 5 Release QuickTime H-264 MPEG4 Part 10 is supported.
You will need to transcode you files into a supported format: Open QuickTime 3, MPEG, Intel Indeo AVI, etc.