I should have known better than giving Windows the benefit of the doubt! I thought WAMP/WampServer screwed things up: suddenly I couldn’t connect to http://localhost anymore. Nor to phpMyAdmin, nor to MySQL.
And because I could connect to the internet, I figured it was my local server…and not a Windows Vista related issue.

However it seems Windows Update, Vista 32-bit, screwed the host-file and the localhost was only reachable via http://127.0.0.1.

Following the instructions from the Wampserver forum solved the issue:
Entering the line 127.0.0.1 localhost, just above the already existing line ::1 localhost.

To actually edit the hosts file in C:\Windows\System32\drivers\etc you have the give your self the proper rights first:
You can do this by right-clicking on the hosts file, selecting properties and the tab Security and selecting Users and pressing the Edit button.
You might give yourself writing rights or full controll: Edit the file and put the original settings back, since you don’t know what Windows might crash next if you don’t!

Hope this helps others out of misery also…and I’m soo close switching OS, when I finish these projects and make enough money to buy me enough time!

PS: I’ve understood the same issue and solution is also applicable for XAMPP.