The problem starts when the site templates have different languages. For example you create a list template in a site with english site template and you upload it to a site with a german site template, you'll not see the template in the create page.
Extract the template file
Now we will modify the .stp file. An .stp file is nothing more than a microsoft cabinet file. Therefore rename the file from "mylist.stp" to "mylist.cab". You can now open the file and see all the compressed files inside.
Afterwards open the manifest.xml in the mylists folder and change the language code within the xml to the destination language code. (See Language Codes )
Open the .ddf file and paste the fallowing code inside:
In the last section write down all the files which should be within the new .stp file. These should be all except the .ddf file.
The result should end in a mylist.stp file within a subfolder. You can now go and upload the new .stp file to the list gallery of your destination site.
Afterwards open the manifest.xml in the mylists folder and change the language code within the xml to the destination language code. (See Language Codes )
Create a new template
In this step we create the stp again. Unfortunately it is not so easy as it seems to be. First of all we have to create a .ddf file. Create a new file in the mylist folder and rename it to "definition.ddf".Open the .ddf file and paste the fallowing code inside:
; DIAMOND Directive File (.ddf)
.OPTION EXPLICIT
; Generate errors on variable typos
.Set CabinetNameTemplate=mylist.stp
.Set Cabinet=on
.Set Compress=on
;The files specified below are stored, compressed, in the cabinet file
30000000.000
manifest.xml
In the last section write down all the files which should be within the new .stp file. These should be all except the .ddf file.
Create cabinet
Open the DOS command promp and go to the mylists folder. Type the following command:makecab /f definition.ddf
The result should end in a mylist.stp file within a subfolder. You can now go and upload the new .stp file to the list gallery of your destination site.
Source: Bari's SharePoint Blog