Adding "Bearer" keyword to POST header return "Internal Exception"

Hi,

I'm getting a very odd failure:

I'm trying to make POST request using invoke url.

i created header map and added 2 key-value pairs (Authorization, Content-Type).

now, when i'm putting the value for the Authorization key as "Bearer hqYUIGEmoTfdWNp54SFRQ8VGz" i get an error 'internal exception' (screen shot attached),

when i'm changing the "Bearer" to anything else the request is sending but obviously i cannot authenticate with the service.

Did anyone expirience this issue and know how to solve?

headers = Map();

token = "Bearer " + thisapp.getToken(); //return string

headers.put("Authorization",token);

headers.put("Content-Type","application/xml");