[Dovecot] auth timeout state=2, bad?

Hello,

we run Dovecot 2.1.7 as SASL backend for our Postfix SMTP-AUTH farm and see this error message occasionally

Oct 22 16:15:32 lxmhs52 dovecot: auth: PLAIN(?,xx.xx.xx.xx): Request 0.21 timeouted after 150 secs, state=2

Since it is mostly the same IP repeating I'm assuming it's a client issue. Is that correct? What could cause this? Can we safely ignore it?

Thanks, Bernhard