If you're still having problems with the LoTRO / Turbine stores I suggest you do what I did: buy it on Amazon.com. It's also 50% off.
Note: the digital download edition at Amazon said it's for Mac only, but ignore it. I run LoTRO on Windows 7. After completing the purchase I received a receipt in the email with the activation code. Just log into your account and paste in the code and it will add the quad pack to your account. No need to download the Amazon downloader or any other software.