Hi

You have given insufficient information - see this post

http://www.magix.info/uk/please-do-the-following-before-posting-your-question.forum.621831.html

In this case look through the error log and see if it tells you where the problem is.  An example can be found in this post:

http://www.magix.info/uk/i-get-encoding-failure-when-i-try-to-burn.knowledge.688510.html

Come back with more information also include the file formats you have imported on the timeline.  If you also have some video clips on the timeline, use GSpot to analyse them and determine if you have the correct codecs installed - use the 1,2,3 buttons bottom left of the GSpot interface window. 

HTH

John