Two possible solutions to this:

1. This sounds like your CAPs have not updated properly to the SP2 files - this update may take a good 24 hours depending on the number of CAPs and your SMS hierarchy. If this error persists, try deleting the contents of the CAP folder/share - NOT the folder/share itself. This will force InBox Manager to rebuild the CAP.
    
2. Microsoft Knowledge Base Article 246331 'SMS: CRC Checking and Installation of Client-Side Hotfixes' gives you some insight into this problem. This problem has been seen on SP2. Verify the client files are in fact build '1493'. Compare them against the server, the CAP, and LP. I learned that the CRC is calculated by the SMS Executive using the client files and stores the CRC in memory. It compares the CRC to the registry, and two files, 'clibase.cfg' and 'cli_inst.cfg'. The 'cli_inst.cfg' is located in three places on the site server:
   
   '\SMS\inboxes\clidata.src', '\cap\clidata.box' and '\smslogon\sites\sitecode'.
   
   The 'clibase.cfg' lives at: '\cap\clidata.box' and '\SMS\inboxes\clidata.src'.
   
   What we did was to rename the 'cli_inst.cfg' file and let SMS build them back. In doing so, this recreated the files and the CRC's now matched what was in memory. This resolved my problem. I had to escalate to Microsoft and the Engineer I worked with is going to turn it in as a bug. Apparently, the 'cli*' files should be updated, but they are not getting the CRC updates.
   
   Verify your client files are at SP2 first or this will not work.