Try removing or disabling BuddyPress. Does this problem still occur on WordPress MU?
I deactivated the BP-plugin. Problem remains. So it’s probably an issue with WordPress MU and the P2-theme?!
Doing more research I found the following thread in the wp-forum:
https://wordpress.org/support/topic/273413?replies=2:
—-
Mippe: P2 brokes äÄ öÖ åÅ letters when editing. That pretty much sums it all up.
noel (Administrator): We’re aware of the issue and will fixing this in the next release.
But I am still unsure: This problem then occurs only with WordPress MU?
You have said that the problem occurs on WPMU, and that it does not occur on regular WP. You have also said this problem is not caused by BuddyPress.
I haven’t got an install of regular WP to test this on, so I am going to assume it is either a WPMU issue *or* you are using an old version of the P2 theme.
I’ll check it. Thanks for the support!
HELP! Since I tried to reactivate the BP plugin I receive a HTTP 500 error when I try to reach the site… mpf!
I deactivated all plugins via phpmyadmin – in the sitemeta-table as well as in the options-table of the single blogs (there are 3 in my installation right now).
So the HTTP-500-Error disappeared. And all of a sudden the P2-theme worked properly as well.
This means: the regular deactivation via backend of the buddypress-plugin didn#t really work. The umlaut-issue with P2-theme seems related to buddypress.
The thing is: I only thought I had deactivated the bp-plugin completely (via backend).
I guess it was removed from the active_sitewide_plugins-field in the sitemeta-table in the database – but it was not removed from the wpmu_sitewide_plugins-field in the same table.
So the site still worked (no HTTP-500-error), and the umlaut-issue with the p2-theme remained.
When I then removed the bp-plugin-entry via phpmyadmin from both fields, the “main blog” didn’t appear anymore (error 500), but the two “sub blogs” I have still functioned. And the one sub blog with the P2-theme worked then without the umlaut-issue.
I hope this clears things up a bit.
So for me it is pretty clear that the bp-plugin somehow interferes with the P2-editor and causes the umlaut-issue.