nukkles

i had cat 3 and upgraded to cat 5 for my network now i have been experiencing intermittent problems. A few times a day, some users lose network connections to the server or the internet. Power supply is clean and constant. im not so sure what 2 look for or what tools 2 use as far as software or hardware tools..... any help would b great im checking the routers and nic card and other little stuff now