I updated to 5.3. Now when I create a new c# file and open it in Monodevelop, it can’t be edited at all. You can’t type anything. you can copy and paste. you can also open a previously created c# script and edit those like normal, but going to “create->c# script” makes and uneditable file. It is not marked as read only.
I suggest creating a bug report, there’s been some instability with the new MonoDevelop in 5.3.
After creating the bug report, post here about it, and add the ID of the bug report to your post (the ID will be sent to the email you used for the bug report, about 15-30 minutes after you send it).
Unity Answers is for helping with script and editor problems. The people who answer the posts are generally just normal Unity users, and usually can’t help with bugs (even if we’d like to!)