As there are a many e-mail questions about the availability of R4, here's is a quick update.
Official explanation is that there is a flash chip shortage. Rumor (HK forums) has it that R4's factories have closed.
Although flash chips are indeed going up as our MP4's are getting more expensive, chips are widely available. We are not sure about the rumor but personally I don't buy the official explanation. All sales and back orders of R4 products are temporarily paused because we are unsure when the item will be back in stock. Back ordered already received will be shipped as soon as R4 is back. Some estimate that it may be in 1 to 2 weeks. If you have a back order that you no longer wish to wait, please send a ticket to us and we will refund your order.
There exist alternatives which are also attractive. The SuperCard DS One Multimedia Card (newer than R4 with extra features). It's in stock and can be shipped within a day from ordering:
http://www.dealextreme.com/details.dx/sku.5097