files in it. During upgrade the files might have been corrupted so create a balnk Sitefinity 4.3.1885 project and copy the .xap files in your Client Bin folder, clear browser cache since browsers cache .xap files and check if you still get the error.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items