Sony Ericsson's Update Service has two fatal flaws. The first is it is not available for OS X (nor are any of their other software packages.) The other is it is it requires Flash version 8 or higher, but when you've got the latest (9.0.1something) it moans (no pun intended).
Sony Ericsson is a major player in the mobile telephone game, they have yet to recognise the Mac market and even basic stuff like update their applications.
It's a good thing their phones are pretty damn good.