You use a Microsoft Lync 2010 Group Chat client to post a text file in a channel.
You post a second text file which has the same file name as the first text file that you posted. The second text file has less content than the first text file.
You use the Open option to download and open the first text file.
After you open the first text file, you use the Open option to download and open the second text file.
In this scenario, the second text file that you open contains the full content of the second text file and part of the content of the first text file.
This issue occurs when a file in a temporary folder has the same file name as the text file that you download. When the Group Chat client user clicks Open to download the file, the Group Chat client replaces bytes in the existing file and then creates a merged file.
To resolve this issue, install the following cumulative update:
2636065 Description of the cumulative update for Lync 2010 Group Chat client: November 2011