Arithmetic operation resulted in an overflow

[esp0]

On a high traffic site, all visitors suddenly got this message:

"   Arithmetic operation resulted in an overflow:
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)\r\n   
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)\r\n   
at WebApiThrottle.ThrottlingCore.ApplyRules(RequestIdentity identity, TimeSpan timeSpan, RateLimitPeriod rateLimitPeriod, Int64& rateLimit)\r\n   
at WebApiThrottle.ThrottlingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)\r\n   
at System.Web.Http.HttpServer.<SendAsync>d__0.MoveNext()"

The problem disappeared after a restart. Is this a bug?