Upgrade of emails doesn't finish. Can't access site

I'm running the latest WP and SBE versions. When I try to access one of my sites it tells me that I have to upgrade SBE and that there are 290 subscribers. When I click to start the upgrade it runs through 290 subscribers and then brings me to a blank white page. I can't access the wp-admin because it always prompts me to upgrade my subscribers. The blank page is truly blank, nothing if I view the source. The SID at the end of the URL is 483, if I change it 482 and hit enter it flashes that 290 were processed. I tried enabling wp_debug but that causes the upgrade to hang around 120.