linkstar going off and on

i activated a linkstar modem and after working for sometime it went offline i.e. having only the power led on, no odu,no sat.firstly i thought it was the odu problem so i took the whole odu and idu to another site on the same network. behold i have the equipments working perfectly well for days.the i took them back to that original site connect and it worked again for sometime went off having only the power led on.i even do fresh cabling but the problem remains the same.this equipments worked at another site but on this said site they are not working okay. so what could be responsible for this problem?could it be the idu or the odu?
please i need suggestions on what to troubleshoot so to get the equipments work for meant site.