Earlier in the day 27/02/2011, my reputation was 3445 and as of evening 27/02/2011 the same has reduced to 3408.
I checked out my reputation graph and there shows no down votes either.
Anyone's got an idea how to track what is going on?
There was a rep recalculation performed on your account. It would've removed rep from questions and answers that were deleted or migrated to another site.
It was a StackExchange-wide recalc done as part of the preparations for the new Users page. More details here on Meta.SO.
See Sudden sharp reputation drop problem: points disappeared and score lost (recalc?) for the details. This was StackExchange wide in preparation for some upcoming changes.