An internal error has occurred

http://ai2.appinventor.mit.edu/#5232643760193536

Suddenly came up against this error. All the blocks have now disappeared, but every time I try to change to the block screen I still get the error message. When I refresh, or reload program, I get the following:

The blocks area did not load properly. Changes to the blocks for screen 5232643760193536_Screen1 will not be saved.

Any ideas? 

I once got this error.

I had too many comment boxes exposed at once

for the browser to handle.

Try minimizing all blocks,

and opening in another browser,

like Chrome.