Strange as it may seem, Maven decided to stop working in Eclipse. I was trying to get an old project up in Eclipse to edit it to use the new Sakai K1 code, and couldn’t import it as an existing Eclipse site. So I used the Maven import function, but had problems (it kept insisting on making 5 projects instead of one with 4 sub projects). I was also having problems with my pom.xml files, so I decided to turn off some options with Maven in the Eclipse settings.
That was my mistake. Something about what I did with the options was very bad, and Maven entirely disappeared from my Eclipse install. No menu, no Window-> Preferences -> Maven category, no resolution of Maven repository, nothing. I tried ripping out maven and reinstalling it, but no joy.
So I just deleted .eclipse from my home directory, and have to start over.
Sometimes I wonder if Eclipse is worth it.
update, the sakai app builder might be the culprit here