The error indicates that you are using fields not existing in the currently loaded data.
Please download and install the latest available Telerik Reporting Q1 2015 Sp1 internal build v188.8.131.522
from your Telerik account - Products & Subscriptions - Latest internal builds - Reporting
. Then run the Upgrade Wizard in all projects having referencees to Telerik Reporting.
If the problem still occurs, please use your support ticket on the same question to send us the problematic report's definition.
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