On install got the same problem in UK host in Germany (+1 hours) 2003 shared server. Did all the Locale stuff and problem persisted perhaps host hasn't got locale installed, anyway ...
Tracked the cookie and noted that the LTVST was being recorded with a , not . I thought this was probably due to a server/database/locale setup, but just wanted to find a solution so checked recording a straight numeric date in the form 12345.123456789 in the cookie and found the . replaced by a comma when read straight out quite bizarre and probably not a locale issue.
This might not be complete fix as I haven't finished testing and it's not elegant but replaced in the following files common.asp, default.asp, active_topics.asp some code as follows.
Replace
isNumeric(Request.Cookies(strCookieName)("LTVST"))
with
isNumeric(Left(Request.Cookies(strCookieName)("LTVST"),5) & "." & Right(Request.Cookies(strCookieName)("LTVST"),9))
and
CDate(Request.Cookies(strCookieName)("LTVST"))
with
CDate(Left(Request.Cookies(strCookieName)("LTVST"),5) & "." & Right(Request.Cookies(strCookieName)("LTVST"),9))
If those who have the problem with cdate and the cookie issue and find anything else to change or if this solves your problem let us know.