A lot of people are mistaking the different regional versions of Google Base. Basically signing into the UK system listing and then go through the US version and seeing no items at all.
Partial blame for this unnecessary confusion is down to Google by not clearly marking and differentiating the different regional versions.
heres a brief overview of the current setup:
UK - base.google.co.uk - items get pushed to base.google.co.uk, then to google.co.uk/products and google.co.uk onebox results
US - base.google.com - items get pushed to base.google.com, then to google.com/products and google.com onebox results
DE - base.google.de - items get pushed to base.google.de, then to google.de/products and google.de onebox results
The most annoying thing i find is that when i log into my google account the Base link under my services takes me to base.google.com.
This is an outstanding issue Google are working on but for the most part its a unnecessary roadblock for most.