Ok done.
Error diagnosed and so far eliminated
It was an application I created at webcasts subsite.
I created an instance of lars-bloger bellow webcast’s subsite and it crashed with another instance on every page that has this instance referred. So when he clicked on flush it refreshed the buffer and the bug showed up.
there was some chunk of code related with lars-bloger pkg, precisesly a call to an instance of the pkg. and because of it it crashed triyng to call it twice.
Some trash code in the pages of the source that I already cleaned up on the page packages/edit-this-page/index.tcl
Then i replaced edit-this-page pkg to i guess the most updated head's version.
cvs -d mailto:anonymous@cvs.openacs.org:/cvsroot co openacs-4
see it: http://www.openacs.org/forums/message-view?message%5fid=435246
and it's working fine! thanks.