problem with playing videos in new Captivate

I face problems with playing inserted video clips. They play fine when I preview in Captivate, but the problem starts when I publish as SCORM and upload to our LMS (Moodle).

When inserted in Captivate as a Video grid block, "No video with supported format and MIME type found." appears in the course (tried in various browsers). When inserted as slide video, some play, some don't, and as a rule, when I insert more than one clip per course, they don't play.  

Videoclips are my own  (created in PremierePro as MP4), ranging from cca 100 MB to 1GB (size isn't the problem - I tested that).

Any idea what could be going on?

Thanks, Petr