There are several Serial Communication (COM port) options available for Lazarus, but I would first suggest giving Synaser another try.
I'm currently using Lazarus 1.2.4 with Synaser from Synapse v40 and even latest trunk revision without any problems.
Alternative COM port implementations:
- TComport port for Lazarus (cportlaz)
- Serial Communications Windows API (CreateFile, ReadFile, SetCommMask, etc)
- more in Hardware Access and Serial Communication for Lazarus