Do in eclipse:
window->show view->other->maven->maven repositories.
One of the indexes is: http://repo1.maven.org/maven2.
right-click on this one, and try rebuild index.
If that does not work, create a new index with the same address, and do a rebuild of that.
With me that worked, and I could remove the original one.
After this a restart of eclipse will NOT show the error anymore, and the add dependency search function operates as it should