I am assuming that you are trying to click on links in emails that you have received as opposed to something like PTC banners within the sites themselves.
If the error you are seeing is like this ...
QUOTE
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@takethemoneyandrun.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
... then generally it will mean that there is an issue with the server where the PTR site is hosted.
If it were
Bandwidth Exceeded or
Account suspended you would see a different error / warning message.
Hopefully the site(s) you are having problems with will rerturn soon once the issues are resolved.
JoeP