I've had that problem. Don't know what causes it. I've been able to fix it by first closing the program's tab in the IDE, then closing the IDE, then reloading everything. There was also one time in which certain keywords were no longer highlighted regardless what I tried, but that was fixed by rebuilding the docs.
Another problem I have is with the auto indents. When you indent a line, then hit Enter at the end of the line, the cursor is automatically indented to align with the previous line. Every now and then, the cursor will go to the beginning of the line and I would have to manually indent every single line. At first, the only way I could figure to fix it was to cut n paste the file to a new document, but I later discovered that if i keep at least one character after the cursor, a space, a carriage return, etc... then the cursor indents properly. What I think is happening is that somehow an end of file marker is accidentally being deleted or something.
Another problem I have is with the auto indents. When you indent a line, then hit Enter at the end of the line, the cursor is automatically indented to align with the previous line. Every now and then, the cursor will go to the beginning of the line and I would have to manually indent every single line. At first, the only way I could figure to fix it was to cut n paste the file to a new document, but I later discovered that if i keep at least one character after the cursor, a space, a carriage return, etc... then the cursor indents properly. What I think is happening is that somehow an end of file marker is accidentally being deleted or something.