Can't login to site & CataLook product lists don't click through to products (looks like a caching issue but PageBlaster is turned off!)

All of a sudden, for no apparent reason (OK, I know something must have happened!) I am getting some very strange behaviour on a site I am developing:

• Noone can log in. There are no login failed messages, the page just refreshes when Login is clicked
  
• On CataLook product list pages, clicking a product to click through to the product detail also just causes the page to refresh.

It looks like a caching issue but I can't figure it out. I have PageBlaster 2.1.2 but the problem persists even when I comment it out in web.config.

What could be going on??

Figured it out ..... I had managed to set the CacheTime property of all of my modules to 1200s. Most modules (like Account Login & CataLook) need a CacheTime of 0 to function propertly. I made this mistake by going into a module settings page for a module that had a CacheTime of 1200 and clicking both Set As Default Settings and Apply To All Modules (in Page Settings > Advanced).

Because I couldn't log in to fix it, I used this SQL script to change the CacheTime to 0 for all modules other than 'Text/HTML' :

update tm
set cachetime = 0
from modules m
join tabmodules tm on m.moduleid = tm.moduleid
join moduledefinitions md on m.moduledefid = md.moduledefid
where friendlyname <> 'Text/HTML'