Sparkfun MP3 shield + RTC

Hi guys, I'm using the MP3 shield by sparkfun ( http://www.sparkfun.com/products/10628). With the sketch from Sparkfun MP3 Shield Arduino Library « The Mind of Bill Porter along side a RTC and some other sensors.
The sketch uses the SFEMP3Shield.h library.

I want to write the time stamp from the RTC to the SD card on the MP3 shield so I guess my best bet is to use the SD.h library. The problem is that I'm having problems with the 2 libraries as they don't play nice with each other. I've tried combining the code from the SD.h to the SFEMP3Shield.h with no success. Anyone with a good knowledge of library and how they work could help me out? Which line in the SD.h controls the read write function to the SD card?

Any advice will be great.

p.s I've tried the example "MP3 Player Example" on the sparkfun site but it seems laggy when playing back MP3 beyond 192k.

Have you tried the work-around on the following page:

http://www.billporter.info/sparkfun-mp3-shield-arduino-library/
(go down to "Using the SPI bus for something else as well")

If this is not your problem, you may have to describe it in a bit more detail.