Can't get imported screen capture TIFF to play back smoothly

Hi There:

We need to produce a talking-head video where the scene shifts back and forth from the speaker to screen shots of caprured web pages. I am creating screen captures using Print Screen button in Windows, saving as a TIFF image, importing into Premier Pro CS5.5. I looks great until I play it, then all the text in the TIFF image degrades and goes jaggy.

Any suggestions re what I am doing wrong, or better ways to do this? I also tried using Snagit made by Camtasia. I create an MPG4 file with Snagit, import into PP but on playing it, it has the same problem... seriously degraded text.

Thanks,

Rudy Pohl

Ottawa