[TYPO3] SQL error for one FE_user login, all others work fine

[Pieter]

Hello group,

one of my FE_USER can't log in.  He receives an SQL error instead.  I 
enabled the debug info and this states:

caller:	
t3lib_DB::exec_SELECTquery
ERROR:	
You have an error in your SQL syntax. Check the manual that corresponds 
to your MySQL server version for the right syntax to use near '3) AND 
(lockToDomain='' OR lockToDomain='www.vivant.org')' at l
lastBuiltQuery:	
SELECT uid,subgroup
FROM fe_groups
WHERE
deleted=0 AND hidden=0 AND uid IN (,3) AND (lockToDomain='' OR 
lockToDomain='www.vivant.org')

debug_backtrace:
require // ux_tslib_fe->determineid // ux_tslib_fe->fetch_the_id // 
ux_tslib_fe->initusergroups // tslib_feuserauth->fetchgroupdata // 
tx_sv_auth->getgroups // tx_sv_auth->getsubgroups // 
t3lib_db->exec_selectquery // t3lib_db->debug

The FE_USER is member of fe_group with uid=3 but all other fe_users of 
this group can log in just fine.

I'm using newloginbox 2.2.11,  kb_md5fepw 0.4.0 and sr_feuser_register 
2.3.3 on Typo3 4.0.

I have no idea why this one user can't log in while all the others can. 
  The username or password does not contain any special characters.

Pieter