Hello Charlie, rate of feed and tension are probably what's giving you problems. Do you know what brand and size of blade, you purchased from Lowe's? How thick is the stock you were attempting to cut, and what type of wood was it? What brand of saw are you using, and how good are the blade clamps? Need answers to these questions, to try to help to solve your issue. For me, when cutting 90* corners, I use the same size blade as I would use to cut out the project. The blade size I use depends on, how thick the wood is. You can't just grab any size blade, and think it's going to cut all thicknesses of stock! I have lots more on say on the topic, but, I would like for you to answer the questions first. Then, I can give you the best answer possible.
Len