Errors in the encryption library: Failed to encrypt sensitive data. Possibly the encryption key is inaccessible because of improper service account change.
1. Stop SSAS service
2. Make backup of project: C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Data\MyProject.0.db
3. Delete SSAS database. So delete contents of C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Data\MyProject.0.db directory.
4. Copy 0.CryptKey.bin file from backup to C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Data\MyProject.0.db
5. Start SSAS service and deplot/process your cube again using BIDS.