Odd RE error at start up - what's the cause?

My hosting provider has is migrating my shell account from BSD to
Linux.  I have most things transferred and working but there's an
annoying message when tin starts up:-

    Reading config file...
    tin 1.8.3 release 20070201 ("Scotasay") [UNIX] (c) Copyright 1991-2006 Iain Lea.
    Error in regex: invalid UTF-8 string at pos. 21 '.\(([Ww]a[rs]|[Bb]y[l³]o):.*\)\
    Reading keymap file...
    Reading input history file...
    Reading groups from active file... 

(I may have tidied a bit too much off the end of that RE)

So where is the expression at "pos. 21 "?  .... and why am I getting
an error, as far as I know the locale is set the same on both the old
and the new system and I didn't get an error on the old system.

-- 
Chris Green