I also just yesterday saw the ‘Shop Offline !’ message for the first time. However, I believe it was due to my host having a ‘hiccup’ on their server as other services were also down. Eventually, just went away.
Only other times I got a complete failure of shop & admin it had to do with permissions in one case and missing module files in the other. Maybe the added module was not uninstalled properly (reference not removed from admin>core settings>modules). Could just try adding the module files back.
although the module kind of old, I reckon the problem has to be pointed to the installed language files. Had/have kind of the same problems (using mud_translation) on this project: http://translate.oxidforge.org with “Slowanian”.