Guillermo Eiland - Adobe Flash Player Error

To answer your question precisely:

Run-Time Errors - Adobe ActionScript® 3 (AS3) API Reference

Security sandbox violation: %1 cannot load data from %2.

That said, I imagine that this isn't super helpful.  It sounds like a misconfiguration on the content provider's side, so there's probably not a lot you can do; however, I'm just guessing, because I don't have the basic context necessary to know what's actually happening.

The list of stuff below would be a great place to start; however, I don't think that there's much you can do from your end but complain to the developer of the website you're trying to use.

https://forums.adobe.com/thread/1195540