May the problem is due to TSCC code though it works fine within AE.
Try converting the .avi to a different codec such as .mov.
You can convert existing TSCC AVI videos to use a different codec by placing the AVI on the timeline in Camtasia Studio. Click Produce and share, select Custom Production Settings, choose the AVI format and then click the Video compression button to choose a different codec.
Vishesh Arora
3D and Motion Graphics Artist
Films Rajendra
Blog:
http://digieffects.wordpress.com
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