500 Error & Theme Error

I am unable to click on SELECT THEME for any of the other themes in the Admin Design area and have it BE selected. Nothing happens. When I DO click EDIT THEME the theme design window opens but Nothing changes when I choose colors, replace the logo (by manually changing the url in the field) or make any other design choice in the editor.

When I click SAVE (to see what happens), I get a blank window in the popup design editor window and a "Internal Server Error - The server encountered an internal error or misconfiguration and was unable to complete your request. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request." Error on the Admin Design Editor page (the one in the background).

I HAVE set the permissions of the /webassist folder and all sub folders to 755. No luck.

I ALSO tried the instructions here and am still getting the same error result:
showthread.php?t=21951&highlight=properties.php

Please help. I have a client on a deadline :) There goes my estimate!

I have created a support ticket so we can look into this issue further.

To view and edit your support ticket, please log into your support history:
supporthistory.php

If anyone else is experiencing this same issue, please append to this thread.

I have replied to the ticket you sent asking you to call Friday Sept 9th but I had scheduled TODAY (Friday Sept 9th here in Australia) to get this up and running for my client. Is there ANYTHING ELSE I can try in the meantime please???

we resolved this on the phone by setting the permissions for all of the files in the webassist/plugins/styler folder to 755

I get the following error when I try to save changes to a theme. I have changed the permissions, uploaded the new styler and properties files and still get the error. Please help. Thanks.

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster@carterlayne.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

I have created a support ticket so we can look into this issue further.

To view and edit your support ticket, please log into your support history:
supporthistory.php

If anyone else is experiencing this same issue, please append to this thread.