Uploading multiple files via SharePoint Multiple files uploads…failed mainly for file extension such .CS and .JAVA these files not in SharePoint 2010 File Block List under central admin.
By the way when you upload single file including .CS/.JAVA ext. no issue.
Notice that the issue happen following actions
1. Upload Multiples files (i.e .CS / .Java) Failed.
2. Windows Explore also fail to upload.
So how to overcome this issue. By removing file extension from IIS request filter allow to upload .CS and .JAVA files.
To help others :
1. Go to IIS
2. Select your website and Find Request Filtering
3. File Name Extensions tab and Select your extension for the list
4. Right click the and Remove.
5. Upload your files via SharePoint 2010.