Ok, good to hear you found the source of the problem. Hopefully XVM will fix this. I really like the fact you are pre-releasing your modpack for CT, that really benefits the speed of release when 1.0 comes out!
With the Aslains_WoT_Modpack_Installer_v.9.23_CT_01 version on the CT server, the settings dialog will no longer close. If I run in safe mode, it all works just fine.
I attached the logfiles.
Aslains_WoT_Logs.zip
It seems that for "Aslain's XVM Mod + ModPack Installer v9.13.42" has a SHA256 that does not match: cd60833f8945cb047a9d33273a86e230eef0bd0976c103a658f9d561fbfa0df9
The one that is downloaded has SHA256: 60d3603414c25108417551a8d8c2432350ffaac03b5db043088b47c8e5d85f96
I tried both links: the "direct" one and the "mirror #1". So the question is: is the installer corrupt? or was the SHA256 not updated?