Sounds similar to what happened to me.
Since it is recognizing the software, at all, it should be fixable.
First try to change the port setting to com 4.
Otherwise:
1. I suggest starting over completely, if you didn't already. I mean unplug the unit from the computer.
2. Then remove the current software installation using "add and remove" menu from the program file pull-down.
3. If you haven't already, download and read the "Windows Vista Driver Installation" from the Icom site:
http://www.icomamerica.com/en/support/kb/Article.aspx?ArticleNumber=7AR9446825
note: looks like a special driver installation is required. I hear tell there is a 32 and 64 version of vista (I use XP Pro, 32-bit)
4. If you feel confident follow the, above, documents directions and reinstall the software onto your PC. (A system restart shouldn't be necessary but it wouldn't hurt.)
5. Plug the PCR2500 into the PC.
6. Turn it on.
7. Start the R2500 program from the Program File menu or by double-clicking the shortcut.
8. Proceed to turn the power on button from the menu and see if this fixes it.
(note: BTW - ensure that you have set the audio switch, in the PCR2500, to the desired position.)
9. If you're still having problems you can verify the port selection in the Device manager under "system info" in the program file menu under "administrative tools" then click on "device manager".
Here you will look for the "ports (COM & LPT)" (this represents the serial port configuration.
click on details and see if the the following is displayed:
USB\VID_10C4&PID_EA60&MI_00\IC-R2500_xxxxxxx_xx (xxxxxxx_xx is your receivers serial number)
note: check the "port" setting in this step (9) as well. click "properties" then "details" under "port setting". It should have picked up port 4 but you may have a different bridge allocation.
10. Also under the device manager look under "Universal Serial Bus Controllers" (USB's).
Here you will look for the following to be displayed:
USB\VID_10C4&PID_EA60\IC-R2500_xxxxxxx (xxxxxxx is your receivers serial number)
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Let me know the turn out
OAK