If you get a screen like the one bellow (see 'Error screen') it means that some requests timed out. At the startup, there are multiple requests sent at a time and some of them require connection to qualityunit.com (check the license and verify if there is a new version available). If the connection to qualityunit.com times out, it times out other requests too. Temporary fix of this issue is to disable network connections in Post Affiliate Pro. If you do so, then some features like adding gadgets or checking new version will not work, but merchant panel will load normally.
To disable network connections in Post Affiliate Pro edit accounts/settings.php
and add following line there:
Where the issue comes from? Well, this is more likely a Curl issue, so it means, that you may have some kind of firewall or some server configuration that does not allow Curl connection to the servers of qualityunit.com.
Here is another example of the screen. I also added screenshot of the Firebug message:
If you can find an animated image on the right of the POST requests, than check it and try to find Gpf_Install_CheckVersion or something similar... If it is there, than this is surely the network problem...