[TYPO3-english] All frontend plugins are not rendering

[Salander]

Hello,

Firstly, I'm crap at english so I hope you'll understand my issue.

After I made an upgrade of an old typo3 website ( 4.1 -> 4.5 ),  all my frontend plugins ( sr_feuser_register, etc...) don't render in the
front-end.
If I insert any FE plugin via the backend, it doesnt show up in the FE HTML; just this.
   
  <!--  Plugin inserted: [begin] -->
   
  <!--  Plugin inserted: [end] -->


Do you know what can cause the trouble? The template maybe?

I really need your help guys, I'm working on this problem since 2 weeks.