Are you running UBCD from an USB stick?
Avira won't work in that cas because it can't find its antivirus definitions. It is a know bug of the Avira Rescue CD. It should be fixed in the next update of the Avira Rescue CD, but it takes a very long time before they update their CD.
Post your exact problem at:
http://forum.avira.com/wbb/index.php?page=Board&boardID=210
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Download
Ultimate Boot CD v5.0:
http://www.ultimatebootcd.com/download.htmlUse
Parted Magic for handling all partitioning task:
http://partedmagic.com/