We recently moved premises and moved our network to a new IP address running 10.1. When I re-started the machine the service were not running, but I could get to the manager. When I re-started ArcGIS Server, I could no longer gain access to the manager or services.
I uninstalled 10.1 and installed 10. SP1 from scratch. I did keep my \arcgisserver directory from when the machine had a different IP address (but the same name) though.
When I start the ArcGIS Server, the two java processes do not start, but the ArcGIS Server process starts. I cannot find any logs that tell me what the problem is.
I had the same issue when upgrading. I also tried uninstalling and reinstalling, with no joy. What I eventually discovered was that the log (C:\Program Files\ArcGIS\Server\framework\etc\service\logs\service.log) was saying (upon startup):
Found flag file C:\Program Files\ArcGIS\Server\framework\etc\upgrade.txt. Starting in upgrade mode.
So I renamed that file to upgrade.txt.old, restarted ArcGIS Server, and voila! Manager and admin page suddenly worked. Problem solved.
I don't know why it wasn't starting, but that at least got me to a fresh, functional installation.
Thank you Loren, I just hit this today & same as you uninstall/reinstall did not work. Renamed the upgrade.txt file restarted ArcGIS Server service and back in business!
