POWER OF ATTORNEY

                                                                    Exhibit 24.2

STATE OF          Illinois         )
                                   )  SS
COUNTY OF         Cook             )

      KNOW ALL MEN BY THESE PRESENTS that Howard Walker, having an address at
Chicago, Illinois, has made, constituted and appointed and BY THESE PRESENTS,
does make, constitute and appoint, or either of them, having an address at Two
North Riverside Plaza, Chicago, Illinois 60606, his true and lawful
Attorney-in-Fact for him and in his name, place and stead to sign and execute in
any and all capacities this Annual Report on Form 10-K and any or all amendments
to this Annual Report on Form 10-K, and to file the same with all exhibits
thereto, and other documents in connection therewith, with the Securities and
Exchange Commission, giving and granting unto each of such, Attorney-in-Fact,
full power and authority to do and perform each and every act and thing,
requisite and necessary to be done in and about the premises, as fully, to all
intents and purposes as he might or could do if personally present at the doing
thereof, with full power of substitution and revocation, hereby ratifying and
confirming all that each of such Attorney-in-Fact or his substitutes shall
lawfully do or cause to be done by virtue hereof.

      This power of Attorney shall remain in full force and effect until
terminated by the undersigned through the instrumentality of a signed writing.

      IN WITNESS WHEREOF, Howard Walker, has hereunto, set his hand this 28th
day of February, 2005.

                                                  /s/ Howard Walker
                                                  --------------------------
                                                  Howard Walker

      I, Jennifer L. Usher, a Notary Public in and for said County in the State
aforesaid, do hereby certify that Howard Walker, personally know to me to be the
same person whose name is subscribed to the foregoing instrument appeared before
me this day in person and acknowledged that he signed and delivered said
instrument as his own free voluntary act for the uses and purposes therein set
forth.

      Given under my hand and notarial seal this 1st day of March, 2005.

                                                  /s/ Jennifer L. Usher
                                                  ---------------------------
                                                  (Notary Public)

My Commission Expires:

      01/06/07