追記・・・
もし開発環境をお持ちならば以下のパッチを試してもらえますか？
*** getchar.c~ Mon May 27 12:23:48 2002
--- getchar.c Mon May 27 12:23:38 2002
***************
*** 1843,1849 ****
* multi-byte char. Happens when mapping
* <M-a> and then changing 'encoding'. */
if (has_mbyte && MB_BYTE2LEN(c1)
! > (*mb_ptr2len_check)(mp->m_keys))
mlen = 0;
#endif
/*
--- 1843,1849 ----
* multi-byte char. Happens when mapping
* <M-a> and then changing 'encoding'. */
if (has_mbyte && MB_BYTE2LEN(c1)
! > (*mb_ptr2len_check)(mp->m_keys) && mp->m_keylen > 1)
mlen = 0;
#endif
/*