Word post more info on your set up. (memory,memory timmings, Videocard, Motherboard, CPU Cooler ect.ect)
Also with benchmarks you normally do them 3+ times and take an average. Also being said It is only a 300mhz overclock don't expect a huge performance increase.
Could be anything like your memory clocks might be even slower at 4.1 then at 3.8
Or even better If your using a stock cooler the CPU could be throttling and actually is running slower then 3.8ghz