Are you sure you meant Gulbis? He was ranked 53 last August, while Murray was ranked 4.
That would make more sense. Checking the USOpen site to check out the info. Ok now i see , i misread the date for the rankings
http://www.usopen.org/en_US/players/overview/atpg858.html
Under the line high rank date for singles, i thought they meant the rank 4 for august 2008, when they meant he obtained his best ranking august the 4th. Doh !
Figured you just misread it.