Mine did the same thing today. A new stapler would likely be cheaper than sending out the the broken one for repair, if you can even find someone to do it. It appears spare parts are not available, either. If the same part broke on yours as mine, which appears to be their most common failure, you might want to give this a try. Since I lack a TIG welder, I used super glue on the broken tab, to temporarily fix it in the proper position, then built up a bead of JB Weld on the inside. As the operating lever is thin, it doesn't appear to require much space in there. I also used vise-grips to hold it to a piece of thin cardboard, and used more JB on the outside corners, making sure not to get any in the notch where the mainspring sits. Since it's here, I did the same on the un-broken side too, to give it a little more strength. It appears there is enough room still, even with the bead on both inside corners, to allow the lever to disengage properly upon tripping. After it cures, I'll file the outside corners as necessary, to allow it to move freely within the groove in the frame. Hopefully, the cardboard will reduce the amount of filing required. Since this part is subject to high impact forces in use, I plan to add another coat on the inside prior to re-assembly, and fill it in as much as possible without interfering with operation. The first coat is curing as I type this, so I'm unsure if this will work. As cheap as I have been lately, it seems worth a try to me. Nice assembly picture @
http://www.fixya.com/support/t13186938-assembly_diagram_5700_power_shot - if you care to try it.