[exim] Problems with spamassassin and exim

Hi list,

as I already mentioned in the thread "Different problems with exim" I've
got some trouble with spamassassin. As the structure of the other thread
has just become a little bit confused, I split it now.

Here is my problem:

I configured exim to ask spamassassin at every incoming mail, wheather
it's spam or not. Most of the time, this works just fine. But sometimes
spam comes unscanned to my users.

In case of error, exim paniclog tells me one of the following lines
(randomizely choosed):

2008-09-16 13:22:29 <mailid> spam acl condition: error reading from
spamd socket: Connection reset by peer
2008-09-16 14:38:22 <mailid> spam acl condition: error reading from
spamd socket: Connection timed out
2008-09-16 12:57:53 <mailid> spam acl condition: timed out writing spamd
socket

And /var/log/mail.warn says:

Sep 16 14:37:52 vs248104 spamd[3833]: bayes: cannot open bayes databases
/var/lib/nobody/.spamassassin/bayes_* R/W: lock failed: Die Datei
existiert bereits

(The last words mean: file already exists)

So, what I want to know is:
1. Is there a way to solve this problem?
2. Can I make exim retry connecting to spamassassin if this didn't work
for the first time, before sending mail unscanned?

I would be pleased, if anyone could help me.

Thank you

Mirko