I was at a customer the other day. We needed to reboot the VC VM the customer hadn't done this in ages, and typically , after the reboot the vCenter server service wouldn't start, I check the eventvwr and found event id 1000. After some Googling I would appear that something was already running on port 80. I checked the VPXA logs in this location %ALLUSERSPROFILE%\Application Data\VMware\VMware VirtualCenter\Logs\ and found this error:
[VpxdReverseProxy] Failed to create http proxy: Resource is already in use: Listen socket: :80
Futher Googling suggested either IIS has been installed, or the SQL reporting service was installed. Some reports suggest that WinRM takes port 80 but this was later found to be incorrect.
I even tried upgrading the customer the vCenter 4.1 U2 this still did not work.
NETSTAT -ANO reported that java.exe was taking the port so I presumed that Tomcat was stuffed.
Fix: In the end I thought I would stop some services to see if that was the cause. Sure enough when I stopped VMware Update Manager, port 80 was then free. I set the VUM service to delayed start and this sorted the issue. A couple of reboots proved this worked! What I can't work out is that know one else had blogged this issue.