Further problems have been experienced at Apple's flagship Regent Street store, where the company has had to install VMware Fusion on some Macs to run Internet Explorer, the only web browser compatible with O2's activation system. Because of O2's own problems, however, people were still initially unable to get their phones properly activated. As a result, a number of customers at both Apple and O2 stores have been forced to leave without an iPhone, though shops such as O2's Bluewater and Glasgow locations have been allowing people to pay and fill out paperwork so they can return later. Anecdotes from O2 and Carphone Warehouse stores indicate that supplies of the 16GB iPhone may be extremely limited in the UK. One Carphone Warehouse employee is said to have explained that each outlet may have only one 16GB model in stock, the rest being 8GB. The crisis follows problems with online orders at O2, which not only resulted in a server crash, but complete sellout of stock within hours.