Infopath SharePoint Library

Hello.

I have an InfoPath SharePoint Library. I have just released it for lots of senior managers to review and it has suddenly had a lot of errors appearing, it was perfect this morning.

1) This appears in multiple browser when I try to view the document (form) library. However sometimes I refresh and it works perfect and others the message reappears. It does seem to help most of the time if I clear the cache. (Ctrl + F5).

"Unable to display this Web Part. To troubleshoot the problem, open this Web page in a Microsoft SharePoint Foundation-compatible HTML editor such as Microsoft SharePoint Designer. If the problem persists, contact your Web server administrator.
Correlation ID:feb7c97a-dd49-4e6a-8d65-b0b2171afdc8"

2) So I open up SharePoint Designer and where the web part is meant to be it says.

"This Web Part does not have a valid XSLT stylesheet:Error: Reference to undefined entity 'nbsp'.

I have used the search function to search the code, (which I haven't touched or written at all) and it only finds ' ' as it should do?

Please help this is urgent.

Thank you very much for your answers in advance.