Sorry, only saw mentions of the Kobo on a few US web sites (reviews, rather than user forums about any problems).
I don't want to be too negative, but am wondering if support is limited to people in N America, following on from the closure of Borders in the UK.
Looking on the page about the Kobo E-Reader, I see it mentions the Sync'n'Read facility. Do you have this software on your PC ?
It is probably worth a search of the Borders website for any mention of restricted to USA only.
I saw such a note on one of the Borders pages about a free (PC-based) e-reader application.
In the past I have used a service called HTTP Tunnel which allows some USA web sites to believe my PC is in the USA (because their servers over there accept my website requests and send them out, giving the final website a USA location... whatever comes back to the HTTP-Tunnel servers then gets passed on to me. I am using their free service, which is a little slow, but for just 'registering' as a user, it seems OK. If you need to download large files it might be too slow - but downloading software may work OK, if you've had a problem with getting/using software.
The Adobe site has a list of supported devices for use with Digital Editions (or is that the wrong s/w) ? But the Kobo is not mentioned.