Zen cart installation / maintenance / customisation / hosting
Supported Modules: Dutch language pack, Multi site, Dynamic Price Updater and more.
It does "look" that way, but because of the error in ZC 1.5.4 that is addressed in the link above, the problem really is that the language id value in the database does not resolve to a value that properly accesses the associated language.
As to sequence, a language pack that doesn't already include an override directory (YOUR_TEMPLATE or similar) can be installed in either order. It is though generally suggested to install a template as the first action and then any template related modifications can be made manually or automatically without affecting the core/classic files.
ZC Installation/Maintenance Support <- Site
Contribution for contributions welcome...