This likely isn't the right board to post this, but here we go.

If I reply to an article or forum post, I'll sometimes get a warning message indicating a 'validation error. If this problem persists, contact an administrator'. This especially seems to happen when it's taken me some time to type up a response.

The only solution is to copy the text I wrote, click on the link to the source article, click 'reply' again and paste in the text, saving it good and fast.

It's been a while since I used Drupal CMS, but I faintly recall having some problems with validation errors under similar circumstances. In my case, as I recall, it had to do with caching -- but this was several versions ago, and may not be relevant in the current version.