[Q] Can't install another ROM

Hey guys,

I currently have Cynagenmod 10.1 running on Galaxy S I9000, but it won't let me install another rom (Liquid Smooth v2.8 for I9000 to be exact) over the top of the existing one.

I am booting into CWM 6.0.2.8 and I have tried the following:

'Wipe data/factory reset"
"Wipe cache partition"
"Wipe dalvik cache"

And then installed the OS from the zip file. It tells me it has installed successfully and I reboot it but when it restarts, it is simply still Cynagenmod installed just with it starting fresh.

I have tried using the boot loader CWM and the one within Droid and it makes no difference.

If you can shed some light, that would be great!

Thanks in advance.

- Ben