Cookies have been auto-deleted?

[#1]

Tried to switch user today from my partner's account (running XP-Prof with fast-switching enabled) but it just sent me back to the Welcome screen.  I restarted.  When I got on to my account, all my Cookies were gone!  Even now, if I click the 'remember me' box or whatever, no cookies.  Anyone got any idea what's caused this and are the two incidents related like I suspect?  I'm the primary administrator on the PC (i.e. I can see all the files, my partner can see everyone's but mine) and I'm running IE6 if that's any help.
Ta,
Dawn.

[#2]

Each user has there own set of cookies, so if you change user thats where they have gone

[#3]

Were the cookies on your own account to start with, or the administrator account? pierre_pierre is right, in C:\Documents and Settings there is a folder for each user, including an administrator, and the cookies for each user are kept in there. Has anyone run anything like CCleaner that might have deleted them?

[#4]

It's not a problem we've had before and we've been running the computer the same way for 5 years.  No-one's run anything new that they know of: it's only me and my partner that use it.  It was fine until yesterday afternoon.  All the settings are still the same (allow cookies etc.) and we've no reason for it to be happening.

[#5]

Hmm, strange. Many cookies have an expiry date after which they stop working, but that wouldn't account for all of them disappearing.
If you look in your cookies folder can you see anything in there? It would be good to see if they have actually disappeared or are just not working. They will be in C:\Documents and Settings\<username>\Cookies
IE6 is out of date now, so there may be some bug there. It was never exactly renowned for its reliability. Try an <a href="http://www.microsoft.com/windows/downloads/ie/getitnow.mspx">upgrade to IE7</a> or use <a href="http://www.mozilla-europe.org/en/firefox/">Firefox</a> instead.

[#6]

No, there's nothing in there except something for Nero (and I've no idea why that's in there); it was the first thing I checked when I discovered they weren't working on the first webpage I used with them (Yahoo! email).  I have noticed Y! does require cookies to work at all though, and it was working fine while the browser window was open: only when it was closed did they disappear, but I think that's normal because our work Intranet works like that (you can navigate elsewhere and back on the same window and it'll stay logged in).
Someone on my LiveJournal's suggested I check the really hard-to-find settings, but if that doesn't work I shall probably give in and reload Windows in general when I get back from Christmas (and then install Firefox and attempt to network two computers: a whole day decoted to disaster!).
Thanks very much for your help