I've not once heard of this problem, and Pandora has been an App partner for several years. I'm surprised, but let's see if we can get this figured out.
Your Pandora App should be linked with only your account.
You might request assistance from Pandora directly, since they would be able to address account issues. email@example.com
The other option is if you have Pandora on a Samsung TV or Blu-Ray player, you can try to reset the device, but then all of your settings will be reset. If you want to go that route, I can assist - just let me know what model you have. (In most cases, holding down the STOP button will effective reset the Blu-Ray players in 2010). Then go back in and link up your account. If this still happens, Pandora will have to address it.
Oddest, and frankly disturbing problem with the Pandora app on my Samsung blu-ray player... I log in, it all works, come back in a day and all my stations have changed, different user is logged in, and I when I log back into my account all MY stations have changed (I assume the app is giving some one else access to my account...) this all but wrecks the app for me, which is a shame as it is very cool... anyone else had this problem.. most odd indeed...
Now I am actually getting obscenely named stations showing up, I think the user I am conflicting with is getting sick of me changing their stations...