The "Select Period" dropdown box of AWStats is created with all the months in the random order in Plesk 10.4.4.
Product issue #PPPM-44, which is fixed in Plesk 11.5.
There is the file which is named
nav.html . It is loaded in the frame in the AWStats home page. Its generation was broken until 11.5 and in the latest version it is fixed - sorted list of months is generated only after all logs processing.
So the solution here is to perform Plesk upgrade to the 11.5 version.