I have a large number of extensions that I keep in sync between my computers with the Addons Collector extension. I've noticed on the last couple of installs that after I add all my extensions I can no longer view my collections on the Subscriptions tab. After much enabling and disabling of extensions I finally narrowed it down to the Personas extension that triggers the blank page under Subscriptions when it is enabled. This has occurred on multiple computers under various operating systems, I'm going to dig into whether its a specific persona causing the issue, but its very strange that I can have a persona applied, disable the extension and the persona remains visible and my Subscriptions tab becomes viewable again.