This one had me stumped for a while:

Customer has dial-up access to the internet, and says she cannot access yahoo and her email.

I figure its probably something blocking the internet connection, eg a connection problem, or a firewall acting up.

Once there, I realise that she cannot access yahoo.com and her yahoo mail… but other websites seem ok.

When trying to connect to yahoo, IE gives an error (I didn’t make note of the exact error, but it mentioned trying again later, check your DNS settings, make sure you are connected to the internet, etc)

Ping yahoo.com.au works correctly.

I notice she is using NIS. I’m suspicious, since I’ve seen norton blocking legit traffic before. Given it has already expired (last update was 18 months ago), I uninstall it… but the problem with yahoo persists.

I figure maybe a bad DNS cache, so i try: ipconfig /flushdns
but still no yahoo!

It must be something with IE… I’m tempted to try firefox… but it would take too long to download.

I look at internet options -> content (but content advisor is not enabled)

I look at internet options -> privacy, but that looks normal.

I look at internet options -> security -> restricted sites (but none are restricted)

I look at internet options -> general, and try deleting all cookies, and all temp IE files (including offline content), and also clear the history. After that yahoo finally works.

I figure there must have been a corrupt entry in the temp cache (or a corrupt cookie), so clearing the cache and cookies, forced the website to download non-corrupt copies.

I install antivir, spywareblaster, and winpatrol, and then my hour is up, and I leave another happy customer.

Update:

I got a call 2 days later… customer can get into yahoo website, but cannot login to yahoo mail anymore. I make an appointment for a second visit, but a day later, she calls to cancel, as the problem has fixed itself (by restarting the PC).