Are severe nocturnal leg cramps sign of any illnesses? Both legs affected. Just switched from Soma to flexeril (cyclobenzaprine hcl) b/c daytime fatigue. Want to avoid Soma

Could be. Many medications can cause cramps, so talk with your doc about the meds you are on first. With nocturnal leg cramps, i'd probably do some basic blood work to check for anemia, as well as your potassium and other electrolytes, thyroid and kidney function. And good for you for wanting to avoid soma (carisoprodol). At the risk of incurring corporate pharmaceutical wrath - I've found it to be an awful medication.
Maybe withdrawal... Soma (carisoprodol) is broken down by the body into a drug called "meprobamete" that has some barbiturate like characteristics. When you stop taking Soma (carisoprodol) it can cause some withdrawal-like syndromes. The bottom line is that if you are experiencing any symptoms after starting a new medication you should contact the prescriber right away.
Yes. Commonly venous disease, with leaky venous valves, resulting in leg swelling, and pain. See a phlebologist to have your legs evaluated.