2000 Chevy Astro Rear wheel locking up

I have a 2000 Chevy Astro van. To preface, the van sat with major emission problems from Dec. 2005 to March of 2008. Four thousand dollars later, dealer, it is back up and running again. Recently though, while driving, the ABS and brake light has randomly come on. I feel no problem in braking. When I restart the van, light is off and does not come back on for a few days. I needed to replace the front rotors and pads a couple of weeks ago, all was fine until 4 days ago. As I was pulling out of my driveway, it felt as if the E-Brake was engaged. The rear wheel locked up and skidded out of the drive. Then loosened up and all was well. As I was at idle speed in a parking lot, it felt like I was feeling a thump-thump-thump. I went to inspect my rear shoes, had a very difficult time getting the drum off, took over an hour. But upon inspection, wear looked minimal, but the shoes were very glazed over and lots of build up around all the hardware. I replaced everything, shoes, hardware, wheel cylinders and drums. I don't know if this fixed the problem because the drums will not go back on. I returned everything and started over, same results. I also know that the same hardware, shoes, cylinder and drums are the correct ones, there is only one option. I am stuck. Any ideas? I finally was able to force on drum on, but it is riding on the shoes. Adjuster is completely closed, no fluid in the cylinder as yet. I am of the opinion that the drum should have slid on relatively easy. Am I wrong? The last time I worked on drum brakes was in 1983. I avoid them, usually take drums brake jobs to the shop. But money is scarce these days for us. Any help would be greatly appreciated. BTW, it is has 2 ABS sensors in the front and one at the tans housing.