I understand that you created a GUI using the third-party GUI Layout Toolbox, and it now crashes GUIDE after your recent Java update. There are a few potential sources of the issue. For issues like this, it is very helpful if you provide what operating system you are using, and which version of MATLAB.
This is especially important because MATLAB transitioned to a new graphics system in R2014b. There are also two versions of the GUI Layout Toolbox, one for R2014a and before, and another for R2014b and later. If you used the Layout Toolbox for the incorrect version, that could be a potential source of issues. Also, if you created the GUI in a different version of MATLAB than the one you are trying to open it in with GUIDE, that could also potentially be causing the issue. There was a Newsgroup thread with a similar error. It was suggested that restarting the computer (to allow Java to rehash everything) might help, and also checking for any custom startup.m files. Enter the following command at the command prompt:
If any files are shown, check to make sure there aren't any changes you don't want being done in them. There really should only be one startup.m file, if any.
It also matters which operating system you are using, and which version of MATLAB. On a Mac, with versions R2013a and earlier, MATLAB uses the operating system's Java Virtual Machine. Later versions include their own JVM shipped with the MATLAB release, just like for Windows and Linux releases. If your MATLAB is using the shipped JVM, the Java update on your operating system should not have affected anything unless you have pointed MATLAB to use the OS' installed Java. See these Answers posts for more information about changing which JVM MATLAB uses for Windows, Mac, and Linux.
If none of these situations seem to apply, I would suggest making a very simple GUI using the GUI Layout Toolbox, and see if that still causes the issue with GUIDE. If it does, I would suggest contacting the creator of the toolbox. If the simple GUI does not cause the issue, you could try deleting features from your original GUI (using the Layout Toolbox) one at a time until the issue does not occur, to narrow down which uicontrol(s) or feature(s) caused the issue.
I hope this helps point you in the right direction!