I am pretty sure this problem is caused by a broken video codec installation on your PC.
iPiStudio uses DirectShow video playback infrastructure and therefor is vulnerable to video codec problems.
Even if you are writing an uncompressed video its playback may be affected by broken AVI Splitter installation. Usually, this happens when you install third-party (non-Microsoft) video codecs.
You can find a summary of the troubleshooting methods for this problem in our Wiki:
http://www.ipisoft.com/en/wiki/index.ph ... leshootingPlease let me know if it helps.
Sorry for this problem. We will work on a more reliable solution in future versions, but it will take some time because we will have to replace DirectShow video playback infrastructure.