I read somewhere that such a thing may happen and it sound very similar to my situation.
This is where I read about it:
No Glutes = No results The Plague of the Mediocre Athlete -
Even the shortest rides and/or walking just one mile causes an over-fatigue on my glutes area. I get immediately tired. I feel like I need to stretch them out really well. It happens even though I am resting myself from cycling for 3 weeks. Has anyone ever been in the same situation?