My mpc cuts a sample during playing :/ whatzz goin wrong?

My mpc has 128mb ram, hard disc 80gb. The problem is:
i`ve filled about 18 tracks with some drums,hats,snares. It sounds good. I`ve recorded a sample from yamaha motif xs by mode/record. then i`ve set this sample to the new program called for example program02 and now its under PAD1. then> mode/grid edit, and sample1 is set to start playin from the beginning. sequence is set on 4 Bars. I switch play, and what happens?:
that sample[4 bars lenght] plays till the end of 1`st bar, but the sampler cutts it in the next 3 bars. Basicly, i can hear it in first bar, but its some kinda muted in the next 3 bars. Memory isnt full, i got 90mb free. Sample dacay is a 0 value, so theres no possibility to fade out itself. When i mute some drum tracks, that sample is bein played till the end. The same situation is with solo. But when an everythin is bein played together, my sample stops at the end of 1 bar. Whats happenin? If Ya dont understand Ill drop a link to my video tommorow.

i`ve found this http://www.mpc-forums.com/viewtopic.php?t=93163 and maybe it explains my problem, i hope it doesn`t!

Sup man, I beleive you are running into the poly voice issue

Definitely. Poly-Voice. You can only run so many voices at once. Try making your drum program mono-phonic if that doesn't f*ck the feel of the drums too much...