<PAGE>
                                                                   EXHIBIT 10.67

SILICON VALLEY BANK

                        AMENDMENT TO OVERADVANCE LC RIDER

BORROWER:         PROXIM CORPORATION

DATED AS OF:      MARCH 31, 2004

         This Amendment to Overadvance LC Rider is entered into between Silicon
Valley Bank ("Bank") and the borrower named above ("Borrower"), with reference
to the following facts:

         Bank and the Borrower are parties to the following: the Loan and
Security Agreement between them, dated December 27, 2002 (the "Loan Agreement"),
the Accounts Receivable Financing Agreement dated June 13, 2003 (the "Accounts
Agreement"), the Amended Overadvance LC Rider dated October 31, 2003 to the
Accounts Agreement (the "Overadvance LC Rider"), and the documents, instruments
and agreements relating thereto (with the Loan Agreement, the Accounts
Agreement, and the Overadvance LC Rider, collectively, the "Loan Documents").

(Capitalized terms used but not defined in this Amendment, shall have the
meanings set forth in the Accounts Agreement.)

         The parties agree as follows:

         1. EXTENSION. Section 2(a) of the Overadvance LC Rider, is amended by
replacing the date "March 31, 2004" therein with the date "May 31, 2004", so
that it reads as follows:

                  "(a) Overadvance LCs may be outstanding only during the period
                  from the date hereof to the earlier of the following (the
                  "Overadvance Maturity Date"): May 31, 2004 or the date the
                  Accounts Agreement terminates by its terms or is terminated by
                  any party in accordance with its terms."

         2. FEE. In consideration for Bank entering into this Amendment,
Borrower shall concurrently pay Silicon a fee in the amount of $5,000, which is
fully earned on the date hereof, is non-refundable and is in addition to all
interest and other fees and charges payable to Silicon. Silicon is authorized to
charge said fee to Borrower's loan account or to any of Borrower's deposit
accounts.

         3. REPRESENTATIONS TRUE. Borrower represents and warrants to Bank that
all representations and warranties set forth in the Accounts Agreement, as
amended hereby, and the

<PAGE>

other Loan Documents (other than the Loan Agreement, the representations in
which were replaced by those in the Accounts Agreement) are true and correct.

         4. GENERAL PROVISIONS. This Amendment, and the other Loan Documents set
forth in full all of the representations and agreements of the parties with
respect to the subject matter hereof and supersede all prior discussions,
representations, agreements and understandings between the parties with respect
to the subject hereof. Except as herein expressly amended, all of the terms and
provisions of the Overadvance LC Rider, and all other Loan Documents shall
continue in full force and effect and the same are hereby ratified and
confirmed.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment to
Overadvance LC Rider as of the date first above written.

Borrower:                                    Bank:

PROXIM CORPORATION                           SILICON VALLEY BANK


By /s/ Michael Angel                         By (illegible)
  ------------------------------               ---------------------------------
      President or Vice President            Title
                                                  ------------------------------


                                     CONSENT

         Each of the undersigned acknowledges that its consent to the foregoing
Amendment is not required, but the undersigned nevertheless do hereby consent to
the foregoing Amendment and to the documents and agreements referred to therein
and to all future modifications and amendments thereto, and any termination
thereof, and to any and all other present and future documents and agreements
between or among the foregoing parties. Nothing herein shall in any way limit
any of the terms or provisions of the Continuing Guaranty of the undersigned,
all of which are hereby ratified and affirmed.

Proxim Wireless Networks, Inc.                   Wirelesshome Corporation

By /s/ Michael Angel                             By /s/ Michael Angel
  ------------------------------------             -------------------------
Name  Michael Angel                              Name Michael Angel
    ----------------------------------               -------------------------
Title EVP & CFO                                  Title EVP & CFO
     ---------------------------------                -------------------------



Proxim International Holdings, Inc.
(formerly Western Multiplex International
Holdings, Inc.)


By /s/ Michael Angel
  ---------------------------------------------------

                                                                             -2-
<PAGE>

Name Michael Angel
    ---------------------
Title EVP & CFO
     --------------------



                                                                             -3-