One of my clients created a twitter post with some wacky characters. Frankly, I don't know which characters they were - they simply displayed as rectangles.
As soon as someone viewed the website, causing your plugin to run the update the options stored in the database (and hence the text from each recent tweet), all hell broke loose.
Due to the non-UTF-8 nature of those characters, the MySQL server didn't accept the remainder of the option string. This, obviously, caused a fatal error on the first chance it could when your plugin would try to retrieve information from it.
I did my own makeshift solution as I was using this plugin for a MAJOR component of a MAJOR client's site (thanks for that by the way), and it was breaking the layout badly. All I did was utf8_encode($tweets[$i]['text']) for all $i in count($tweets) before you added them to the $options array for updating.
Look into it, it's a pretty big issue. Looking forward to your next update having it - I hate having to hack solutions. Thanks!