The error resulted from the space not being found so end = -1.
FILE: pubs/default/lenya/content/search/search-and-results.xsp
LINE# 515
ADD: the bounds checking code

                          if(slfield.length() > excerptOffset){
                             int start = 0;
                             int end = excerptOffset;
                             int half = excerptOffset/2;
                             if(first < half){
                                end = tmphtmlbody.indexOf(' ', excerptOffset);
                             }else{
                                start = tmphtmlbody.indexOf(' ', first - half);
                                end = tmphtmlbody.indexOf(' ', start +
excerptOffset);
                             }
//BEGIN: bounds checking (prevents StringIndexOutOfBounds if end = -1)
                            int tmphtmlbodylength = tmphtmlbody.length();
                            if(start > tmphtmlbodylength) start =
tmphtmlbodylength - excerptOffset;
                            if(start < 0) start = 0;
                            if(end < start) end = start + excerptOffset;
                            if(end > tmphtmlbodylength) end = tmphtmlbodylength;
//END: bounds checking
                             tmphtmlbody = tmphtmlbody.substring(start, end);
                          }