Sony Ericsson has angered existing smartphone owners over a recent decision to freeze firmware updates for the P990i smartphone, M600i communicator and W950 music phone.

Sony Ericsson's head of product management, Niklas Sivander, confirmed the decision on a developer's forum:

"These firmware releases meet the requirements of bug fixes prioritized by our operator customers and the customer services organization within different markets."

"The decision to freeze the P990, W950 and M600 firmware versions at this point has been made based on meeting these requirements."

The new UIQ3 user interface on the new Symbian 9.0 operating system was problematic and very buggy, particlarly on the P990i, leading to the need for firmware upgrades, and despite serveral being released for the handset, is still described as having "serious shortcomings".

Sivander explains: "Sony Ericsson, however, underestimated the complexity of the development work for UIQ 3 and it took longer than expected to implement and quality assure things like the platform security mechanisms, the multimedia framework and other advanced connectivity aspects like 3G, videotelephony and Wi-Fi. It has been a tough journey for all of us".