$ perl -F, -lane '@F % 2 and push @D, [@F] or push @{$D[-1]}, pop @F; }{ $,=q{,}; print @{$_} for @D' input.txt

##</code><code>##

1/3/2007 12:20:01 AM,12.588309,9.432586,20:0.196329,7.418672,3.616305,2.066482,6.873061,0.784989,1.859894,3.249620,0.450952,0.305768,0.823402
1/3/2007 12:49:22 AM,10.958312,13.644527,41:0.483233,7.027840,4.222601,0.305821,7.443877,1.552915,1.202711,5.285398,0.233119,0.425521,0.560862

##</code><code>##

$ perl -MData::Dumper -F, -lane '@F % 2 and ($k)=@F or push @{$D{$k}}, @F; }{ $D{$_} = {@{$D{$_}}} for keys %D; print Dumper \%D' input.txt

##</code><code>##

$VAR1 = {
          '1/3/2007 12:49:22 AM' => {
                                      'ClientAdd' => '1.552915',
                                      'CMALoad' => '1.202711',
                                      'SearchDelete' => '0.305821',
                                      'CMASave' => '5.285398',
                                      'ClientDelete' => '0.425521',
                                      'CMADelete' => '0.233119',
                                      'Login' => '10.958312',
                                      'SearchCount' => '41:0.483233',
                                      'SearchDetails' => '7.443877',
                                      'Logout' => '0.560862',
                                      'SearchResults' => '7.027840',
                                      'SearchSave' => '4.222601',
                                      'SearchLoad' => '13.644527'
                                    },
          '1/3/2007 12:20:01 AM' => {
                                      'ClientAdd' => '0.784989',
                                      'CMALoad' => '1.859894',
                                      'SearchDelete' => '2.066482',
                                      'CMASave' => '3.249620',
                                      'ClientDelete' => '0.305768',
                                      'CMADelete' => '0.450952',
                                      'Login' => '12.588309',
                                      'SearchCount' => '20:0.196329',
                                      'SearchDetails' => '6.873061',
                                      'Logout' => '0.823402',
                                      'SearchResults' => '7.418672',
                                      'SearchSave' => '3.616305',
                                      'SearchLoad' => '9.432586'
                                    }
        };