So, I'm doing the Battle For Windhelm mission on Skyrim. I made my way to the palace with Tullius and Rikke. I went through the whole spill with them and I picked the option of Tullius killing Ulfric. After that happened, my game auto saved and the Battle For Windhelm was considered complete. This is where the problem starts. Right after that, Tullius and Rikke start attacking me. The doors in the palace are locked, so there's no place for me to run off to. I've tried putting away my weapon, the calming spell is too weak for them, I've tried actually fighting them and all I do is get them down until they regenerate their health and they start attacking me again, and I don't have any previous saves that I can load. I'm completely stuck and don't know what to do.

I'm playing this on Xbox 360. Please help!

reload your autosave from when you entered the city and fight all over again. Can't explain why they are hostile to you.

check if you have a bounty.

I think you probably do have one so... after taking over windhelm the imperials are now seen as the guards so they will attack you and try to arrest you. Tullius and Rikke can't arrest you so they will just try to kill you.

If you do have a bounty then reload a save from before starting the quest so you can pay of the bounty.