None of our concrete sites (version 5.3.3.1 and 5.3.2) have a viewable dashboard page. We are getting the following error:

PHP Notice: XML error: EntityRef: expecting ';' at line 5, column 75 in C:(website aaddress)\httpdocs\concrete\libraries\3rdparty\simplepie.php on line 1801

We can still view pages within the dashboard though (for example, index.php/dashboard/settings is viewable to the user).

Renamed the current simplepie and uploaded the 1.2 version in concrete/libraries/3rdparty and still didn't work.

Our 5.3.3.1 sites seemed to be working fine prior to 1/11/2011 in the afternoon, not sure when it broke exactly. All 5.4.x sites are working properly.