Internal link - strange error

[maeg]

Hallo

When I want to make an internal link, I experience a strange error on a few of the websites I host, but not in all of them.

[ external image ]

I can make the link and it works well.
But I do not understand why this error comes.
I've read the thread below, but can not see how I solve the problem.
http://www.cmsimpleforum.com/viewtopic. ... 1228#p6891
http://www.cmsimpleforum.com/viewtopic. ... e9a#p13763

I hope someone have the magic words