You fix an interlacing issue by using the correct settings at each stage during the process. I know that sounds like a useless answer, but its the best one I can give. You need to determine the interlace (or progressive) settings your camera uses, and stick with them throughout the entire editing process to avoid issues. Interlacing is a tremendous pain in the neck, but its how video works so we are forced to deal with it.
You cannot change the project settings once the project is created in EffectsLab. This is another reason it is important to get the settings correct. However, in order to not lose all the work you have done, please see this knowledgebase article.
As detailed there, you can use presets to transfer all the work you did to a project with the correct settings, so you don't have to start over from scratch.http://fxhome.com/account/programs
Its worth visiting that page to make sure you have the latest version of EffectsLab installed.
As far as the sound glitch thing, what render settings and codec are you using? Does it make a difference if you try a different codec, or if you try different render settings?