This feed including the "&" might not be quite correct but other feedreaders do accept it!
The error says:
"HungryFEED can't get feed. Don't be mad at HungryFEED. SimplePie reported: This XML document is invalid, likely due to invalid characters. XML error: XML_ERR_NAME_REQUIRED at line 59, column 28"
There you can find the ampersand. So the "&" problem comes from SimplePie which is called by HungryFEED.
Shouldn't there be a way to put a filter...