as the error message states, there could be a problem with the SM-PC1/SM-BCR2 unit. as a test and if i had access to another unit, possibly from a friend, i would swap them. if not i would take the unit to the nearest shimano dealer and have them test it. should be conclusive and not too difficult. i would check for latest firmware (driver) updates too, if that possibility has not already been explored.

i'm assuming you are familiar with this page from Shimano concerning the SM-PCE1/SM-BCR2?

that type of message is often one that hints to a firmware update/software incompatibility problem. the OS detects (successfully) a device has been plugged into the USB port, passes off control to the proper device driver and then everything goes belly-up. it's often the best message that can be sent under the circumstances.

my sympathies , installation/compatibility problems can often be a SOB.