A Manhattan federal appeals court overturned an award of $900,000 to Steven Arnold, a convicted rapist who said correction officers at the Nassau County jail failed to protect him from a severe beating by other inmates.  The 1999 award was overturned by a three-judge panel of the Second US Circuit of Appeals.  A new trial was ordered on the grounds that the US District Court judge hearing the case, Frederic Block, had improperly allowed the jury to determine the meaning of the working of state law on jail staffing rather than explaining its meaning to the jurors.  While Arnold was being held for trial at the county jail in East Meadow, he initially claimed he and other sex offenders were singled out by correction officer for beating by other prisoners because they were given ill-fitting uniforms that were too large, and that officers had given other inmates at the jail a newspaper clipping about the rape.  The allegations were disproved during the trial at US District court in Brooklyn.  The $900,000 award was based partly on the fact that correction officers, in violation of state regulations, were not present inside the cell area where Arnold was severely beaten.  That resulted in severe injuries to him, including nerve damage, and required placement of a metal plate in his head.  Arnold is serving a 5 to 15 year sentence at the Mid-State prison in Marcy near Syracuse for first-degree rape.  He was turned down for parole twice and is eligible again for a parole hearing in December, according to state records.