You need to firstly ensure that you have the latest DPM 2010 QFE rollup installed and the agents updated in your environment as this can sort out a number of these type of issues with little hassle. Here's a link to the latest QFE:
If that doesn't sort it, you may well have an issue with the SQL collation on your SQL server. Check out the post below, although it's referencing SQL 2008, it is worth checking on your own SQL 2005 server.
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