As an isolated mention on the dev list a while back, I decided to add a debug output on error return from xmlParseMemory in helper.cxx to see the whole string that is failing in the call...

Here are a few lines:

Entity: line 1: parser error : Opening and ending tag mismatch: bookmark_value line 1 and root
okmark_value>Solver for Nonlinear Problems;Options&lt;/bookmark_value&gt;</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
okmark_value>Solver for Nonlinear Problems;Options&lt;/bookmark_value&gt;</root>
                                                                               ^
DBG> <root><bookmark_value>Solver for Nonlinear Problems;Options&lt;/bookmark_value&gt;</root>
Entity: line 1: parser error : Opening and ending tag mismatch: emph line 1 and root
olations and only if those are equal, it measures their current solution.</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
olations and only if those are equal, it measures their current solution.</root>
                                                                               ^
DBG> <root>If <emph>disabled&lt;/emph&gt; (default), the BCH Comparator is used. It compares two individuals by first looking at their constraint violations and only if those are equal, it measures their current solution.</root>
Entity: line 1: parser error : Opening and ending tag mismatch: emph line 1 and root
braries worst known solutions (in regard to their constraint violations).</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
braries worst known solutions (in regard to their constraint violations).</root>
                                                                               ^
DBG> <root>If <emph>enabled&lt;/emph&gt;, the ACR Comparator is used. It compares two individuals dependent on the current iteration and measures their goodness with knowledge about the libraries worst known solutions (in regard to their constraint violations).</root>
Entity: line 1: parser error : Opening and ending tag mismatch: emph line 1 and root
t;/emph&gt;, the library is simply filled up with randomly chosen points.</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
t;/emph&gt;, the library is simply filled up with randomly chosen points.</root>
                                                                               ^
DBG> <root>If <emph>enabled&lt;/emph&gt;, the library is simply filled up with randomly chosen points.</root>
Entity: line 1: parser error : Opening and ending tag mismatch: emph line 1 and root
es (as given by the user) are inserted in the library as reference point.</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
es (as given by the user) are inserted in the library as reference point.</root>
                                                                               ^
DBG> <root>If <emph>disabled&lt;/emph&gt;, the currently present values (as given by the user) are inserted in the library as reference point.</root>
Entity: line 1: parser error : Opening and ending tag mismatch: emph line 1 and root
 known solution as well as the possibility, to stop or resume the solver.</root>
                                                                               ^
Entity: line 1: parser error : Premature end of data in tag root line 1
 known solution as well as the possibility, to stop or resume the solver.</root>
                                                                               ^
DBG> <root>If <emph>enabled&lt;/emph&gt;, an additional dialog is shown during the solving process which gives information about the current progress, the level of stagnation, the currently best known solution as well as the possibility, to stop or resume the solver.</root>


There seems to be various issues with the vtag processing.

Pour info, I'm using libxml2
>#define LIBXML_DOTTED_VERSION "2.9.2"