I found the same problem. I believe it was the fix listed in the CHANGELOG as:
Fixed bug with topic-specific blocks not showing up on the article page when
URL rewriting was enabled (bug #401) [Dirk]
I temporarily fixed the problem by commenting out the change in lib-common.php around line 806 in function COM_siteHeader()...
PHP Formatted Code
if( empty( $sid ) && $_CONF['url_rewrite'] )
COM_setArgNames( array( 'story' ));
COM_getArgument( 'story' ));
By commenting these lines out, you can now edit your StaticPages.
I haven't had time to actually determine why this is a problem yet and hope to spend a little time this evening trying to figure it out so I can get both the staticpage edit working and the problem solved that this code was originally trying to fix.