I had installed (when i had subsciption) Momentum Template with gantry.
Now one year after the install i added a module for instagram and i get the following error:
Uncaught exception: [WARNING 1549] failed to load external entity "/home/clpebunl/public_html/language/el-GR/el-GR.xml" (in n/a - line 0, column 0) [WARNING 1549] failed to load external entity "/home/clpebunl/public_html/language/tr-TR/tr-TR.xml" (in n/a - line 0, column 0) [WARNING 1549] failed to load external entity "/home/clpebunl/public_html/language/en-GB/en-GB.xml" (in n/a - line 0, column 0) [WARNING 1549] failed to load external entity "/home/clpebunl/public_html/libraries/rokcommon/config/joomla2_5.xml" (in n/a - line 0, column 0)
I have contacted the people that i got the module from and they searched and told me that the problem is with gantry framework.
i can now replicate your issue locally and it's not the gantry framework itself, it's an issue related with rokcommon which is needed for both rokgallery and roksprocket. on a test site without rokcommon, i do not get any error.
i also noticed though that when i set 'caching' = no caching in the instagram module settings, i could safely enable rokcommon, roksprocket and rokgallery and did not have any issues.