I feel your pain ... right now I think I am in 4.0-4.5 purgatory. I was not challenged at 4.0, now that I am a 4.5, I am pretty sure I am not good enough for 4.5.
We used to have much more of that here. Players were frequently moving up one year and down the next. Some of it I think was due to players getting bumped and then "working" their way back down to the level where they think they belong.
Recently however, I do not think that is as true. Someone on the boards referred to this as "downwards stickiness" ... but I think the USTA has tweaked thier algoritym to make it harder to move down than it is to move up.
"You should be playing linebacker, not singles."