I'm sure it's just a clich, since for whatever reason the general onsale date never appeared on the ticketmaster page. Since the u2.com presale page is just a mirror image of what's on ticketmaster it's also disappeared from the u2.com presale page. They're probably just correcting the page.
I just received that periodic email that u2.com sends out and they still list the Houston show as going on sale:
From the email:
Concerts On Sale This Weekend and following
Sep. 20 Chicago, United Center
Sep. 21 Chicago, United Center
Oct. 03 Boston, Fleet Center
Oct. 04 Boston, Fleet Center
Oct. 07 New York, Madison Square Garden
Oct. 08 New York, Madison Square Garden
Oct. 10 New York, Madison Square Garden
Oct. 16 Philadelphia, Wachovia Center
Oct. 17 Philadelphia, Wachovia Center
Oct. 19 Washington, DC MCI Center
Oct. 20 Washington, DC MCI Center
Oct. 24 Detroit, Palace of Auburn Hills
Oct. 28 Houston, Toyota Center
Oct. 29 Dallas, American Airlines Center
Nov. 01 Los Angeles, Staples Center
Nov. 02 Los Angeles, Staples Center
Nov. 16 Tampa, St. Pete Times Forum
Nov. 18 Atlanta, Philips Arena
Dec. 19 Portland, Rose Garden