BUG - lose cuelist control

This is the third time I've encountered this over the last year and its a weird one.

Sometimes when programming, the console appears to be working fine, front panel is responding and DMX is outputting.

However you cannot save changes to cues or add new ones, well that's not quite true, you can update cues and you can merge into existing cues, you can also add new cues BUT the changes dont save to existing cues and although the new cues appear in the cuelist you cannot goto them.

The only way to get control back is to quit the show and log back in at which point any added cues have disappeared.

It's totally odd, this time it happened after I sucked the values out of an existing cue (cue 9) and tried to save them to a new cue 12.