I'd advise you get the Mp2x player, which is an updated version of the included player.
The internal player played 90 % of what I threw at it, but the odd file had the skipping
your talking about, when I used Mp2x that played those files perfectly.
I'd also like to sing the praises of GMenu2x, which allows you once you got a shortcut to the player, to
choose the overclock, so if you get a file that's still skipping then overclock to 220 or 240 Mhz and that
should solve the issue. Note though, that apart from the odd file (like 1 out of 10) I've found that using
Gmenu2x and mp2x that most files (even those big full resoultion ones) can be played whilst underclocking
the system to 175 Mhz or so, which is great for saving batteries, so I always underlock and only clock it
back to 200, or 210 when a file is jumping etc.
hope you get it sorted