People picker error: "There was an error in the callback"

[What you have]:

 The error "There was an error in the callback" in the people picker.

[What you want to do]:

 Refer to People picker : can't see the users from different domains.

Don't want to jump to another post ?

Here is the anwser:

stsadm -o setapppassword -password

stsadm -o setproperty -pn peoplepicker-searchadforests -pv "domain:DnsName,user,password" -url {you web application \ site collection URL}

If this doens't help,
make sure that you ran the following command on every WFE:
stsadm  -o SetAppPassword  -password