As for teh Excalibur, the core info up above's proper ... Manatech attempt, lead was extracted at the same time that they figured out that it just flat-out didn't work... exec over the project panics, then throws good money after bad, trying to hammer it together as the planned release date was right around the corner and the rush job bungled it. Early releases hit Desert Wars and were disasterous (with money being spent to send 'runners in to gather dead guns that were discarded, as well as black teams to snuff teh ones who would have given it bad feedback, gobs of Matrix activity to hunt down any negative discussions and recraft them positive ... just a waterfall of money where it didn't belong.
Initial sales were good ... for about a weekend. And then the returns started and customer reviews lit up the Matrix. The jig was up, Ares advertising had wrapped the entire reputation of the corp around teh gun and it failed, BADLY. Like, Edsel bad. Like Homermobile bad. It was *so* bad that the failure cascaded acorss teh corp, to where people didn't trust the name anymore. I heard of people whose smartlink blew the gun up, how do I know my Ares commlink won't blow up in my hands? Can I trust a GM-made car to not drive me off a bridge? Etc etc etc.
There's thought that some of teh people behind it might have intended for failure ... that there were Headcses, or bug infiltrators, or even exec infighting involved to drive the spike into the ground... with teh stock dipping, Vogel or Knight or someone else could sweep in and pick up a controlling chunk. It could also have been a competitor corp using influence to slash Ares' throat. It could have been leftover Seraphim striking in teh name of Cross, or it could have been plain ol' hubris and flawed humanity.
Market Panic will probably say more, of course. Until then, feel free to speculate!