It's not a problem with inc_func_common.asp, it's a problem with topic.asp. You should review the changes recommended by the mod to topic.asp, specially those related with this block of code:
(...)
rM_YAHOO = 5
rM_TITLE = 6
rMEMBER_ID = 7
rM_HOMEPAGE = 8
rM_LEVEL = 9
rM_POSTS = 10
rM_COUNTRY = 11
rREPLY_ID = 12
rFORUM_ID = 13
rR_AUTHOR = 14
rTOPIC_ID = 15
rR_MESSAGE = 16
rR_LAST_EDIT = 17
rR_LAST_EDITBY = 18
rR_SIG = 19
rR_STATUS = 20
rR_DATE = 21
if CanShowSignature = 1 then
rM_SIG = 22
Make sure all the numeric values are not repeated and increase by 1 from line to line.