[exim] RSET - non-mail command?

Here's what I see in logs sometimes when relaying mail from my CGP
backend through exim-based relay server:
2006-12-11 10:50:23 SMTP call from mail.hw.ru [194.67.32.240]:43236
I=[194.186.94.241]:25 dropped: too many nonmail commands (last was "RSET")

According to RFC 2821, "RSET" is absolutely valid command.
Please explain me what to do.

--
Dmitry Pryadko
hosting.rbc.ru