Errors in system log: Magento is unable to load MageRewards templates
You might see a white page when MageRewards is enabled or errors, but if you see the following in your log:
Warning: Mage_Core_Block_Template::include(/home/.../public_html/magento/app/design/frontend/base/default/template/rewards/customer/sidebar.phtml) [function.Mage-Core-Block-Template-include]: failed to open stream: No such file or directory in /home/mepha/public_html/magento/app/code/core/Mage/Core/Block/Template.php on line 212
or something similar, it means your design configuration is incorrect.
This is due to your incorrectly configured Magento design settings, but we have instructions that can help MageRewards adjust to find the filesa regardless. Sometimes people incorrectly set their package to base. Did you do this? If you set your package to base, Magento will use the default package as your concrete package. If you have already started developing the default package and don't want to change this even though it will likely cause issues for you in the future, then you need to follow thje instruction in the MageRewards wiki installation section that talk about moving MageRewards to your custom design package.
Are you using the base package and default theme (default settings)?
If you set your default package to "base" and hit "save" in Magento, some stores experience a bug with Magento where it no longer looks in default/default before looking in base/default. If this occurs you could either fix the db entry, which will have to be done every time you modify/save the package design page, or you could copy your MageRewards theme files to the base package with this guide: Installing MageRewards Into A Custom Design Package. Here is the SQL if you decide to do the DB update option:
DELETE FROM `core_config_data` WHERE path = 'design/package/name' AND value = 'base'