VBA, 121113 characters
Adding my 2 VBA cents...
Function t(s)
k=Right(s,Len(s)-1)
t=Round(Len(k)/2)
If t>0 Then If Left(k,t)=Right<>Right(k,t) Then t=1 Else t=t(k)
End Function
This returns a 1 or 0.
Usage is MsgBox t("abcbcc")
, or to get a "True"/"False"
outsput, use MsgBox CBool(t("abcbcc"))