I have an error coming up constantly:

"Device storage full, unable to send or receive messages."

However:

1) When I try to delete messages through the Conversations application, not all of them are able to be deleted. They don't disappear after being deleted. Sometimes even clearing the conversation doesn't work.

2) RootFs is showing up as 70% used, and 30% free. So I don't see how this is an issue.

Is there a way to manually delete the messages in conversations through terminal??

A re-flash is not an option, since my USB port broke (in the same fashion as all the others).

I would like to know this as well. I use n900 to manage several server farms and these machines may send up to hundreds of sms per day. It was tedious to delete these messages one by one.

I dont understand why that happens when you have so much free space in rootfs. it should be possible to delete them with the x-terminal if you know where the messages are located. I think i saw them once somewhere in /usr/share but ill check back and let you know

Ok, i found out how to manually delete conversations from terminal

delete /home/user/.rtcom-eventlogger/el.db and reboot. That is it.

As far as I know that also deletes your call log. I suppose you could just delete the sms records using an sqlite command

sqlite3 /home/user/.rtcom-eventlogger/el.db "delete from Events where event_type_id in (7,8)"

Use just 7 to delete incoming only. I suppose you could also delete a certain sender's only (say that pesky nagios) with

...where remote_uid = "nagios number" and event_type_id = 7