Can't even open up the site anymore, crashes on page load. Crashes Safari web content every time.
Are you able to access the website from another browser? And to clarify, you load http:.//www.todoist.com and it crashes Safari?
Please try clearing the cache for Safari and trying again.
Yes, it's all messed up, only in Safari. Chrome is ok. The URL resolves to https://todoist.com/app?v=187#start and safari web content crashes and I get page reload errors. Tried restarting and clearing cache but same result.
Did you install any plugins recently, any updates to Flash or similar web related items? Anything that might have changed when this started happening?
Also, what version of OSX are you running?
No, no new plugins. Flash updated a while back, but Todoist.com was working fine a day or so ago. I went premium in the meantime, maybe that had an effect? I'm on 10.9.
Unfortunately I am not able to reproduce this issue. Clearing of the cache for Safari should resolve issues such as this, but as you said, this was done already.
If you have any plugins installed, I would suggest disabling them to see if it resolves the issue, and turn them back on one by one to find out which is causing the issue. Also, check within Safari's settings to see if it's accepting third party cookies, though this should not cause crashes.