Engine Error before menu

Trying to play Gmod. After the blue loading bar, before it gets to the menu, it will crash to desktop with the following Engine Error:

Invalid file id for
C:\program files\steamapps
ath2008uk\garrysmod f\resource\closecaption_english.dat

I didn’t know what to make of it, but went and checked the folder out and such folder nor file existed. Created the folder and copied said file from the TF2 GCF into the folder, yet still get the error.
Going to try and verify TF2 to see if it helps.
Any help deeply appreciated.

EDIT

According to the validation of TF2, all 17xxx files failed to validate, so I must apparently download all 3.229 GB of it, even though all the GCF files are perfectly intact.