You may want to try a Terry Butterfly saddle, or how about taking the saddle off your comfort bike and giving that a try?

Also, have you tried wearing a pair of padded biking shorts?

Sometimes, there's also just a break in period. You may want to try short rides, of say, 5 miles a day for a while until your body adjusts.

The saddle on my bike is one of the cheapest you can buy on the market. I have to wonder whether the reason I never had any problem with soreness, or adjustment period is because I cross-train -- lots of yoga, light weight training, step aerobics, etc. Maybe some good yoga stretches before riding might be helpful.