After a long day at work yesterday, I was closing out tabs and got an error popup when I switched to the tab with my WordPress dashboard. Invalid something... I just clicked to get out, shut down, and go home. Now I can't login anymore. DOH!! I think the only thing I did on that site that day was update plugins.
The site is: http://helpwithyourwater.com/
I've run down all the possible solutions I could find:
cleared cash, made sure cookies were enabled
deactivated plugins by renaming folder via ftp
restored theme with previous backup
updated site URL
ripped out hair
As a result of my tinkering or the initial problem (I'm not sure), the home page loads, but all the subpages give 404 errors.
Any help would be greatly appreciated.