It looks like your thread is a little old and not sure why no one has answered. It is possibly you wired these 3way switches incorrectly. This is called a dead-end 3way the way you have it wired, which is fine if wired correctly.

From what you are explaining, it sounds like Switchbox 1 has one "feed in" and no "feed out" to other devices in the house(besides the 3wire going to Switchbox 2) and also a "switch leg" to light. I will assume this is the case for my explanation.

First off let's make sure you wired correctly.

Switch box 1:

Black from "feed in" should tie to the white on the 3wire. White from "feed in" should tie to white on "switch leg" to light. Black and red from 3wire are your travelers and should connect to the appropriate two screws on your 3way switch. The black from the switch leg should connect to the common screw on 3way switch. In most cases, I would assume you did this last step wrong on each switch. The common screw is usually black, but read back of switch or directions.

Switch box 2:

Black and red should connect to appropriate two screws on 3way switch. White should connect to common screw on 3way switch.

As for your dimmer switch, not sure unless there is a "feed out" of switch box 1 that you wired incorrectly. If there is a "feed out", black should be tied to black of "feed in" and white of 3wire. White should tie to white of "feed in" and white of switch leg. Report back.

If the switches worked when they were out of the boxes and failed after you screwed them into their boxes, a connection may have failed under a wire nut. Since you have a hot indication on the load side of the dimmer, the failure may be in a neutral connection at one of the three-way boxes. Check everything under the wire nuts, a stripped end that has broken off is not uncommon.