Record with these key fields exists!

Hi!
I'm registering item prices in the information register to have an ability to calculate latest ones. I made a document which mades records to periodical information register. But sometimes I receive the following error:

Check, that there are not repeating set of demensions (including Period) at RegisterRecordsCollection of Document during posting.
This error appear when document try to write the same data (set of dimensions) to information register.

The other reason is that you are trying to post document with the same items as was already posted this day (and periodicity of information register is "Within a day")

I've got the point, there really was two rows for the same item in one document and some documents containing the same item prices and the same time...