On Mon, 12 Nov 2018 17:26:52 +0100
andre_debian@... wrote:

> Hello,
> 
> When I clik on a Web link in Kmail,
> I receive this message :
> "you must close Firefox to be linked to this web address".
> (Firefox is already open).
> 
> I go to Trinity Control Center :
> Components of TDE => Default applications
> "Web navigator"
> I erase the information "firefox" and put it again.
> It works, Firefox accepts to open, even if it is already open.
> 
> After some days, Firefox refuses again,
> and same operation above described...
> 
> Bug ?

More likely a bug in Firefox than one in TDE, methinks.
Does adding the  -no-remote option to the Firefox command help?

E. Liddell