I’m afraid I have the same issue with the same version, and also after upgrade to Version 2.5.1.5.
WP version 3.1.3
On another site and host I use version 2.5.1.2 and have no problems.
After save the page returns to an empty template without any errors.
I’ve found out the problem: W3 Total Cache is the culprit here. Turn it off and the newsletter will save…
Sadly, I havn’t installed W3 Total Cache but the issue remains so it’s not likely to be the problem for me. In fact, I’m not having any cache plugins activated.
I could only advise you to try de-activating all plugins one by one to see if there is any conflict.. I’ve found that on some sites it works, some not, depending on the plugin situation.
Good luck.
