Strange network dropping out problem

Hi – We have a weird problem –

We have about 35 users on one floor, the ethernet ports on the wall lead back to a patch bay (on the same floor) each cable leads to another patch bay about 30 metres away – each port is then directly connected to a switch.

The weird thing is that some of the connects drop out occassionally – and changing the patch cable sorts it out.

Could this be a static build up or something similar – if so how do we avoid it.

Thanks for any advice!!

P.s. we have about 80 users on another floor that are not affected.