LT don't work again when re-install the LT extension neither re-installing Chrome

Hi there!
I removed LT extension from Chrome and added again but always appear this message:
“If you have just installed or (re-)activated this extension, please reload the tab first in which you want to check a text.
A page reload may also be necessary when the extension has just been updated in the background.”

I reloaded many times the tab, unistalled and installed Chrome, uninstalled many times LT extension also.
But LT always show the same message.
Any help?
thank you

Hi, on which page exactly does this occur?

I tried to check in our own Web site, but also, to be sure the error wasn’t only on it, I tried in a text box from here,
I can’t send you a link from our Web because it’s private.
It only occurs in one PC. Some days ago LT extension didn’t worked fine (I really don’t remember which error gave), so we uninstalled the LT extension. Since that, always appear that message to reload the page. It’s on windows XP.
On the other pc works fine and some are XP too, but others not.
Thanks to answer!