SQL error with large attachments

I've just installed Roundcube and I am very impressed. But I have noticed one very annoying bug. Whenever I try to open an email message with a large attachment (over ~1Mb) a get a bunch of SQL errors. The text of the message opens fine, but the attachment tries to open as unencoded garbled text. The SQL error messages I get are:

DB Error in .../mail/program/include/rcube_db.inc (129): DB Error: unknown error DB Error in .../mail/program/include/rcube_db.inc (204): DB Error: unknown error Query: (created, user_id, session_id, cache_key, data) VALUES (NOW(), ...[and the rest of the message text ...]

Is there an easy fix for this, or is it something to do with a SQL limitation?

I'm using v0.1-20051021

j.