WP 2.6.1 cannot save a “long” post!!!!

HI all,

I recently upgraded to 2.6.1 the newest version, and then i got this problem:

when i try to post a long article(more than 500 words),after I clicked the “Save” or “publish” butoon, the page turns to a BLANK page, then I refreshed the page, the post which I was trying to post was only left a few words instead and the comment is automatically closed.

I did deactive the all plugings, and changed the theme, I even deleted the Temp files and cookies of the IE7 but problem still there.

and I tried to add a .htaccess file into the wp-admin directory with codes below:

<IfModule mod_security.c>
SecFilterInheritance Off
</IfModule>

but it’s not work as well.

I mailed my host HostIcan, and they said it’s a problem of wordpress.

So now, I have no idea what should I do.

I will really appreciate if i get some tips here. Thank you!

Regards
Frank