It could be caused by a few things. Is the computer going to sleep mode? Check your power saving options.
Also, from the tray icon ( lock icon in the lower R corner ) right click, and select "View Log".
Do you see any entries about bad sectors?
-- If so, the software will pause encryption if bad sectors are found, because this typically indicates hard disk failure. You may also find bad sector errors in the Windows Event Viewer. If you see them in either place, I recommend first running checkdisk (chkdsk cmd)... If that doesn't resolve the issue, you may need to replace the disk. If you experience this issue, and the computer is new, you may be able to get it replaced under warranty.
Best of luck,
Phil