At 280 I've ridden:
Lower-end bike shop mountain bike
Nishiki Sport
Downtube Folding bike (no suspension)
Russian Folding bike from the 60's (smallest and heaviest bike in the stable).
Biggest mods were raising the handlebars on all of them to alleviate wrist pain. The Nishiki (road bike) needs stronger wheels than what was on there.
If you haven't read the first few paragraphs from the link in my sig - any frame will hold you, it's the wheels you'll have to pay most attention to.
If you have little flexibility you may be more comfortable on a mountain bike/touring/cyclocross bike to start off with to have a bit more upright riding position. Stay away from racing frames as they tend to have geometry geared towards the most power but not necessarily comfort. In my sig there's a few good threads on the differences between bikes with pros and cons.