I don't think this will work. I own a Xperia X10 Mini Pro myself and I've also had troubles getting the 2.3.4 update (2.3.3 came on the phone). Unfortunately Wine won't do (esp. such an old version) but you'll need to get VirtualBox Oracle binary edition, get their VB additional modules etc. Then install a Windows guest and flash normally. Worked for me after a lot of "hacking" around with my arch :(
