Creating Clustered Index uses all my tempdb space. Why?
Although you had SORT_IN_TEMPDB = OFF, that is not the only thing that uses tempdb.  You also had set ONLINE = ON.  

Since the job ran 50 minutes before you had trouble, it may be that you had enough activity in that single transaction to fill tempdb with row versioning data.  This is described here:

http://technet.microsoft.com/en-us/library/ms179542.aspx

In part it says: "Online index operations use row versioning to isolate the index operation from the effects of modifications made by other transactions. ... Concurrent user update and delete operations during online index operations require space for version records in tempdb."

EDIT: Actually a 200 MB tempdb seems quite small for a database with a 44 GB table.