The first day that Sun Microsystems allowed users to buy access over the Internet to its long-delayed public utility computing grid, a denial of service attack has forced the company to take down one of the grid's services.

The attack hit a text-to-speech application developed by Cepstral, hosted on the grid, to which Sun had offered access to anyone. To deal with the attack, Sun moved the service so that it can now only be accessed by registered Sun users who are logged onto the Sun Grid as a registered user, Sun said.

Sun initially expected to introduce public access to the grid last year but a series of delays pushed back the actual launch until Wednesday. Sun blamed a variety of factors for the many delays, including security concerns expressed recently by the US Department of State.

The service launched this week allows anyone to order usage of the grid over the Internet, paying via PayPal. Users pay $1 per CPU per hour.

Sun announced the names of enterprises who are already buying access to the grid through contract deals. CDO2 uses the grid to allow customers to run complex financial simulation spreadsheets, and Applied BioSystems is using the grid to reduce the computing time from months to days for certain data research. Sun has also donated 100,000 CPU hours on the grid to Princeton University as part of an education grant program.