I'm experiencing this issue - I'm using CMSMS on my site, where the pages mostly consist of source code, which is highlighted with GeSHi (thanks to streever and calguy1000 about that)

Anyway, when I need to insert code in the page I do it as follows - click on the checkbox Turn WISIWYG on/off at the bottom of TinyMCE and for example put this code there:
Code: Select all
{geshi lang="php"} {literal}
if ($test) {
echo 1;
}{/literal} {/geshi}
Code: Select all
{geshi lang="php"} {literal} if ($test) { echo 1; }{/literal} {/geshi}

Is there any way to fix this? Perhaps using a different editor?
Thanks!