OK... I got mine to work!
1. removed infcache.1 , that didn't fix my problem at first
2 and 3 below were done to remove previously installed (but failed) driver
2. removed ggsemc.sys from windows/system32 and similar directories
3. removed 2 .inf files that both contain ggsemc.sys , and the 2 corresponding .PNF files
(my problem may be that there are 2 .inf files for the same driver... but who knows)
4. started up device manager
5. connected phone with 'c' key depressed, 'Sonyericsson USB Flash' showed up in device manager, with a yellow exclamation mark. Double-clicked it and then "update driver"
That did it. I tried the driver clean-up steps several times before reading this thread, and it didn't work. So I do think the infcache.1 file is the key.
commando , maybe you want to try cleaning up the drivers and try what I did. Good luck.