Seems this script is working fine.Can you just send across your drop table script.

select ' drop table ' + name

from dbo.SysObjects

WHERE LEFT(Name,5) = 'CustA'

AND SUBSTRING(NAME,LEN(Name)-4,3) IN ('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec')

AND DATEDIFF(mm,'2007-11-01',SUBSTRING(NAME,LEN(Name)-4,3)+ ' 01, '+SUBSTRING(NAME,LEN(Name)-1,2)) < 0