Sometimes, you may get an error "The attribute key cannot be found when processing:" in SSAS.

Yesterday, am able to deploy the cube in the SSAS server. Banggg, it's not working now.

Reason for this issue : Mostly, the issue revolves around the duplication of data in to your table.

Step 1: Check for the duplication of data (Remove if it's available)
Step 2: Reproces the cube and deploy it in the server.

For additional reasons, you can check this URL (http://toddmcdermid.blogspot.in/2009/01/ssas-quick-reference-attribute-key.html)

Cheers,
Venkatesan Prabu .J
Head, KaaShiv InfoTech