What exact steps did you use to save this file, please? What browser and operating system are you using? If you create a new file with just a rectangle and save that, can you open that via File, Open from, Device (if not, please attach the file)?
The problem is that all XML in the file is lowercase, which is invalid. Please find attached is a corrected copy of the file. Please answer the above questions to help us resolve this problem in case there is an error in the software, as this is a critical bug. Thanks in advance!