problems with modem after memory upgrade

recently installed 128 mb (pc 100) memory to boost my system to 256. for some reason, modem is not working properly. it was working fine before and i had previously installed other memory for upgrade. from 64 to 128, no problem. from 128 to 192,no problem. i can hear the modem dialing, trying to connect but not successful. do I need to reconfigure modem?