Okay, I've narrowed the problem some more. It seems to be CPU utilization related. When the CPU utilization is at 4% (RR at idle) all girder functions work, volume up, volume down, next track, previous track, etc. As soon as I start playing music, CPU utilization goes up to 28-34% and girder stops responding.
This tells me it's not a com port issue, but something else. My motherboard is a SP13000 (1.3Ghz VIA CPU), I thought this should be adequate CPU power. Hmm.
I tried using igorsfh56 plugin with girder but had zero success with it and that includes configuring igorsfg56 plugin input for DCD mode. Only winlirc plugin + winlirc 0.6.5 running in the background works for me.
If I had high cpu utilization, like 90-100% then I could understand why girder would fail, but mine fails at 34%.