I was trying to publish a Captivate (in Captivate 6.0.1.240, Mac) project both to YouTube and as mp4 but received the following pop up error message:
I have published most videos successfully (to YouTube and in other formats). The particular project is longer than others (about 8 minutes) and of an odd ratio: 1101x752. (I noticed once previuosly that when I received the same error trying to publish another project of this ratio to YouTube, when I adjusted the ratio to the YouTube preset, it published. I didn't try this with this video as it is much longer and the adjustment distorted the video too much to be useable.)