This is a known issue.
For More Information see: Edit Layout/Report in Pro 11 Screen turns to gray when using either of the scroll bars.
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
Thanks, I did not see any related to OS 10.8.1 and FMP11.
Is there are will there be a fix?
That's not a question that I can answer. I'm just a fellow user so I have no "inside information" on upcoming fixes and FileMaker Inc. does not publically announce future fixes or features for upcoming releases of their products.
The problem has persisted through more than one release of the Mac OS.