Joint Filing Agreement

                             Joint Filing Agreement

         Pursuant to Rule 13d-1(k)(1) promulgated under the Securities Exchange
Act of 1934, as amended, the undersigned agree that the Statement on Schedule
13D to which this exhibit is attached is filed on behalf of each of them in the
capacities set forth below.

Date: November 3, 2003

                                  HARBOURVEST PARTNERS, LLC

                                  By: /s/ Xxxxxx X. Xxxx
                                     -------------------------------------
                                  Name:  Xxxxxx X. Xxxx
                                  Title: Member

                                  /s/ Xxxxxx X. Xxxx
                                  ----------------------------------------
                                  Xxxxxx X. Xxxx

                                  /s/ X. Xxxxxx Zug
                                  ----------------------------------------
                                  X. Xxxxxx Zug

                                  HVP V-DIRECT ASSOCIATES LLC
                                  By: HARBOURVEST PARTNERS, LLC
                                  Its Managing Member

                                  By: /s/ Xxxxxx X. Xxxx
                                     -------------------------------------
                                  Name:  Xxxxxx X. Xxxx
                                  Title: Member

                                  HARBOURVEST PARTNERS V-DIRECT FUND L.P.
                                  By: HVP V-DIRECT ASSOCIATES LLC
                                  Its General Partner
                                  By: HARBOURVEST PARTNERS, LLC
                                  Its Managing Member

                                  By: /s/ Xxxxxx X. Xxxx
                                     -------------------------------------
                                  Name:  Xxxxxx X. Xxxx
                                  Title: Member