New plugin installations now jams the plugins section

Hi!
I have approx 10 plugins successfully installed. However now I am in an akward situation where all new added plugins jam the plugin activation panel. It goes like this from the main panel:

plugins-install.php page is jammed at all time now
plugins.php becomes jammed as soon as I add any new plugin (via ftp, as always)

If I then take the just installed plugin away, plugins.php works again.

However Plugins-install-php does not work at all. I remember that last time I was there I tried to insert my server data (so I could use automati install) but must have got it wrong. I suspect this is causing the jam.

How could I erase that data now that I do not even “get in”?

Thank you for any response!