I bought a QuickSSL certificate and installed in on my box and it's run great for over a month.

I just purchased a second QuickSSL certificate for a different domain on my box. The weird thing is that when I enter the https://www.seconddomain.com it redirects to the first domain I created a certificate for. Cpanel shows the two domains listed and I see the keys/certs in the SSL manager

I have tried reinstalling a few times, rebooting and still the same thing happens which is very strange.

Do you have both accounts on different IP addresses? You can only use one certificate on one IP address on one account.