[Typo3-install] Couldn´t unsitall/install extensions

[Xatucans]

Hi, I developed some month ago my site in typo3. I did it in my local server
and when finished my work I moved it to a remote server. The site works fine
in the remote server, but now, I want to make some modification in my web, I
want to implement a forum section and I installed WEC_Discussion Forum
(wec_) extension (I tried this extension before in other site I developed
and it was very easy to install and manage).
The installation looked fine, the extension folders and the DB tables was
created like usual, but when I tried to insert a content element with this
new plugin it did not appear in the pluging list, neither in Ext Manager's
Installed Extension List. I tried several configurations, but it didn't
work. Finally, in my desperation, I tried to uninstall an other extension I
had installed before and I could verified it wasn't possible uninstalling
it. I don't now what is happen, it looks like if the extension manager is
"blocked". Can anybody help me? thanks