Is this on both chainrings?
There are also at least two version of the Shimano 105 derailleur, the version 5501 is 8 and 9 speed compatible, the version 5600 is 10 speed, you may have the wrong model fitted?
http://www.chainreactioncycles.com/M...x?ModelID=2654
http://www.chainreactioncycles.com/M...?ModelID=13595