Word comes from AltaVista that the Add URL page is having a "puzzle" introduced this week to make it more difficult for automated submission tools to use it. AltaVista estimates that 90 percent of the submissions it receives are spam, primarily coming from submit robots.
As always, this statistic does not mean that AltaVista considers 90 percent of those who submit to be spammers. Rather, it's generally that a relatively small number of people generate a huge number of low-quality submissions.
When the new system goes live, visiting the Add URL page will generate a unique submission code for you to use. This will need to be entered along with up to five URLs that you wish to submit. Afterwards, a confirmation will appear.
It's not clear whether you will be prevented from submitting more than five URLs per day, per site, which has been AltaVista's normal limit. I'm waiting for the new service to actually go live, then I'll follow up with more details from AltaVista directly.
AltaVista Add URL Page
Use AltaVista Search Index: Add or Remove a Page box to submit to the crawler. Of course, this may change when the new system is posted.