Context:
I've tried updating from the 5.1.2 update (December 11th edition) to the 5.1.2 update (December 13th edition) but I couldn't access the server after.

Steps to reproduce:
1. Ensure that no builds are running on the server.
2. Pause the system through the "Administration tab" > "System setting" > "Pause system?" option.
3. Take a manual database backup through the " "Administration tab" > "Database backup" screen.
4. Shutdown the server (server.bat stop)
5. Uninstall the server (server.bat remove)
6. Delete the current installation folder of quickbuild-5.1.2 (which dates from December 11th).
7. Download and extract the new 5.1.2 version of QB (which dates from December 13th).
8. Restore the backup from step 3 (with restore.bat).
9. Install and start the server.
10. Open a browser and access the server's dashboard.

Observed results:
The server's dashboard page will fail to load (no connection could be established to the server).

Also note that when booting the server in console mode, I get the following exception repeated a few times:

jvm 1 | 2013-12-13 12:39:29,341 INFO - QuickBuild server started.
jvm 1 | 2013-12-13 12:39:29,343 INFO - You can now point browser to 'http://wn-qb-master-01:80' to access the server.
jvm 1 | Exception in thread "pool-1-thread-2" com.pmease.quickbuild.QuickbuildException: System is now paused and new builds are not allowed to run.
jvm 1 | at com.pmease.quickbuild.DefaultBuildEngine.requestBuild(DefaultBuildEngine.java:1389)
jvm 1 | at com.pmease.quickbuild.DefaultBuildEngine$5$1.run(DefaultBuildEngine.java:1672)
jvm 1 | at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
jvm 1 | at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
jvm 1 | at java.lang.Thread.run(Unknown Source)