Lag playing *.MTS files through VLC and Windows Media Player

[PeeluckyDuckee]

Why is that the case? I am using the Sandisk Ultra SDHC card and recording in 1080/60p mode. Is it because the SDHC card's write performance is not up to par? Once I convert it to *.MP4 format the lag/frame skipping is no longer apparent. I am using the Panasonic HDC-SD90 if that has any relevance. Computer is 2011 iMac on SSD.

Thanks for any insight.