Widgets disable themselves on every new post

Hi, we keep getting the same error in which both our widgets we have enabled will deactivate themselves when we post a new piece of news. We’ve been getting this error since WP 2.2 I can’t find anyone else with these problems does anyone know of a cause. As far as I can tell it isn’t a plugin which is causing it as it still does it with no plugins enabled. The only error in the error log is this one, which seems to be happening quite alot…possibly the cause?

[19-Jun-2007 00:35:04] PHP Warning: strtotime() [function.strtotime]: Called with an empty time parameter. in /home/coop/public_html/incomingsound/wp-includes/link-template.php on line 75

Any help would be massively appreciated, as its starting to really annoy us having to turn it on again and again..
Cheers,
Ed