If you convert a texture pack (In this case I used FaithfulVenom v2 32x) with the program on mojang.com into a resource pack, put it into the resourcepacks folder and try to switch to it, it lags for like 3 seconds and then it doesn't switch. Just stays on the default resource pack.
MC-18228
Resource pack not working
Resolved
Fixed
1
(Unassigned)
Unconfirmed
converter, resource-pack
Snapshot 13w24b
Snapshot 13w25a
Retrieved
Can't reproduce, it works here with that texture pack. Please attach a copy of your console output.