Sorry for my english at first =)

Have a trouble - when trying to place some sound, videos or pdf's at gallery page and then open that page in browser i've got either an error - Page not found or blank page.
Extensions selected for Sounds and pdf's. If i select Sounds and select the folder which contents a sound file in Files, i've got that error. If i select folder which contents no sound - page loads as it must be loaded. I've specified height and width in assets as it said in Documentation for Gallery(filled them with 40 both).
When i check Pdf's in Extensions and don't fill width and height(default 0), page loads. If i fill them with any value - error again.
Any ideas what could be wrong and how to fix it?