Like Bill said, a good T-1 should be error free, but if you happen to be in an area with a lot of new construction, there are a lot of hands in the telco/provider's network. As your provider said, if the ckts were not under a microscope, you probably wouldn't have noticed. All it would take to cause those errors, if they are coming from the t1, is for someone to cross you with another ckt for just a second while wiring up another customer at a dsx location (not much room between pins) or they could be from a mux in the telco/provider's network, switching paths for some reason.
Are both t-1s taking errors or just one of them? Also, you might want to double check the settings for timing on your csu at each end. It's possible that your csu is reporting what is known in t-1 language as frame slips, as frame errors, which are caused by the timing getting off.
Hope that helps some.
