Had the same thing happen to my Shadow back in July. Running on the freeway, and then the RPM just dropped...all the way down to zero. Waited about 3-4 minutes, and it started again. It did this until I got it back home.
Determined it was a fuel feed issue, and pulled the inline filter. It was loaded with junk from my old tank (the rusted out one someone tried to Kreem without prepping it first). Got it home, took the reserve tank out and flushed it as best I could, went to NAPA and got another inline filter, and put it all back together. It's been problem free ever since.
I also got some new hoses to put in place of the old ones, just in case it was a cracked fuel line problem. It wasn't but better safe than sorry.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.