[exim] Strange problem with MySql lookup

Hi all,

i have a strange problem with an MySQL lookup;
many, many lookups work without any problem then I get errormessages like

2006-10-03 17:02:39 H=horn02.intern.ebewe.at (horn.intern.ebewe.at)
[172.16.5.102] sender verify defer for <removed_by_me!>: condition check
lookup defer
2006-10-03 17:02:39 H=horn02.intern.ebewe.at (horn.intern.ebewe.at)
[172.16.5.102] F=<removed_by_me!> temporarily rejected RCPT
<angiola.aloisio@???>: MYSQL connection failed: Unknown MySQL Server
Host 'saxophon' (1)

after exim restart everything is fine

Here is my exim version:

Exim version 4.63 #1 built 04-Aug-2006 13:50:24
Copyright (c) University of Cambridge 2006
Berkeley DB: Sleepycat Software: Berkeley DB 4.0.14: (March 13, 2003)
Support for: crypteq iconv() OpenSSL Content_Scanning Old_Demime
Experimental_SPF Experimental_SRS
Lookups: lsearch wildlsearch nwildlsearch iplsearch cdb dbm dbmnz dnsdb
dsearch mysql passwd
Authenticators: plaintext
Routers: accept dnslookup ipliteral manualroute queryprogram redirect
Transports: appendfile/maildir/mailstore/mbx autoreply lmtp pipe smtp
Size of off_t: 8
Configuration file is /etc/exim/exim.conf


and the config parts

hide mysql_servers = saxophon/rt3/exim/
RT_MAIL_HOST = saxophon
RT_ENABLED = 1

..... and in Routers:

rt_correspond:
  driver = manualroute
  transport = remote_smtp
  condition = ${lookup mysql{select 1 from Queues \
                               where (CorrespondAddress = '$local_part' or 
CommentAddress = '$local_part') \
                and Disabled = 0}{1}fail}
  route_list = * RT_MAIL_HOST

----------------------------------------------------------------------
Wolfgang Fuertbauer (e-Mail: Wolfgang.Fuertbauer@???)
EBEWE Pharma                          
Mondseestrasse 11                     
4866  Unterach, Austria
Tel +43 7665 8123 315    Mobile: +43 664 8397987
Fax +43 7665 8123 1487
http://www.ebewe.com