MadRiver

it is the editor.js file associated to your theme.

/forum/styles/prosilver/template/editor.js

This solved part of the problem for me. However I wanted to use an advanced editor like TinyMCE so it is easier for my users to edit their posts.
With Tiny editor turned off
https://i747.photobucket.com/albums/xx117/derrick_young1/tiny-off_zpsa1ba8c19.jpg

With tiny editor turned on
https://i747.photobucket.com/albums/xx117/derrick_young1/tiny-on_zpsa7438c46.jpg

What I am after and I get if I turn wp-united theme integration off
https://i747.photobucket.com/albums/xx117/derrick_young1/want_zps7c4935ad.jpg

Add me to the List of people getting this error.

I had it working fine for a week or so then all of a sudden it crapped out with this error

@martin_wray1 does cros posting work too for you. I thought it was working but can not get Blog posts to show up in forum

Thank you for the workaround! I have given it a try and will test tonight

Same Problem here. checking the wp-united support board there are reported cases of this going back to August 24th unresolved.

PHPbb installation I have the following installed

Post Count Requirements
phpBB Invite
WP-UNITED

I am running 2.6.1 in wordpress, was 3.6.0 but upgraded to see if that would resolve issue

[b]WP-United Version[/b]        :     0.9.2.5-r0
[b]WordPress Version[/b]        :     3.6.1
[b]PHP Version[/b]              :     5.3.13
[b]WP-United enabled?[/b]       :     Yes
[b]WordPress Home URL[/b]       :     https://san.it/
[b]WordPress Base URL[/b]       :     https://san.it/
[b]WordPress Plugin URL[/b]     :     https://san.it/ised/all/ele/
[b]phpBB URL[/b]                :     https://san.it/ments/
[b]Plugin Path[/b]              :     /are/hidden/for/safety.some/ised/all/ele/
[b]WordPress Path[/b]           :     /are/hidden/for/safety.some/
[b]phpBB Path[/b]               :     /are/hidden/for/safety.some/ments/
[b]Active plugins[/b]           :     bbpress-admin-bar-addition/bbpress-admin-bar-addition.php, bbpress-new-topic-emailer/bbpress-new-topic-emailer.php, bbpress-post-toolbar/bbpress-post-toolbar.php, bbpress/bbpress.php, brankic-social-media-widget/bra_social_media.php, feedwordpress/feedwordpress.php, fwp-sic-em/SicEm.php, gd-bbpress-tools/gd-bbpress-tools.php, wordpress-importer/wordpress-importer.php, wp-united/wp-united.php
[b]Current theme[/b]            :     Good News
[b]Allocated memory[/b]         :     37584.003898635M
[b]Memory limit[/b]             :     256M
[b]Locale[/b]                   :     en_US
[b]integrateLogin[/b]           :     1
[b]showHdrFtr[/b]               :     REV
[b]wpSimpleHdr[/b]              :     1
[b]dtdSwitch[/b]                :     0
[b]phpbbCensor[/b]              :     1
[b]wpPageName[/b]               :     page.php
[b]phpbbPadding[/b]             :     6-12-6-12
[b]xposting[/b]                 :     1
[b]phpbbSmilies[/b]             :     0
[b]avatarsync[/b]               :     1
[b]integcreatewp[/b]            :     1
[b]integcreatephpbb[/b]         :     1
[b]xpostautolink[/b]            :     0
[b]xpostspam[/b]                :     all
[b]xpostforce[/b]               :     -1
[b]xposttype[/b]                :     excerpt
[b]xpostprefix[/b]              :     [BLOG]
[b]cssMagic[/b]                 :     0
[b]templateVoodoo[/b]           :     0
[b]useForumPage[/b]             :     1
[b]wpuxpostcomments[/b]         :     0

As cool as dragging blue dots around the screen is I think simple dropdowns would get the job done cleaner