The hotfix you said is for Microsoft SQL Server 2008. So it will not work on your scenario since you are using SQL Server 2008 R2.
Based on the limited information, we cannot give you the exact reason that cause this issue. In order to narrow down this issue, you can apply the latest Service Pack and Cumulative Update as GregGalloway said. Besides, you can troubleshoot this issue by
using the Windows Event logs and msmdsrv.log.
You can access Windows Event logs via "Administrative Tools" --> "Event Viewer". SSAS error messages will appear in the application log.
The msmdsrv.log file for the SSAS instance that can be found in \log folder of the instance. (C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Log)
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