Right after creating a clean new site (no other plugins running yet) I added a TLD name with upper case letters in it -- why, you ask? I just copy-pasted the domain name from the clients e-mail where he used capitals to make the three words combined in the name stand out -- and set it as primary domain.
After that, the site was no longer accessible. Chromium reports:
Error 310 (net::ERR_TOO_MANY_REDIRECTS)
Opera just keeps on loading nothing...
I went into the network admin and after editing to all lower case after which the site became accessible.
Just thought I should mention this :)