I have a 6600 firmware 4.09 and when I try to install 1.6.1 the installer comes up then dissapears. Same problem i had with 1.5.1. How come this will not work with firmware 4.09?
I had problems with many programs while using 4.09.1... upgrading to firmware 5.27.0 let's me install much better. so far i have been able to install all that i want with 5.27.0.
if you can use windows, you could install pc-suite and connect the phone using mrouter tick box in com-port (mine was 3) and then connecting to bt-serial port with your bt-software.
then if you can see the "link" icon in mrouter, or the "two computers" icon, you know that the symbian framework is connected between your phone and computer. then you can just double click the sis file in computer, and it starts to install it to phone.
For me, the programs that i couldn't install in 4.09.1, installed with pc-suite/symbian framework every time.
if you have linux or can't use pc-suite, and the primary way for you is to copy the sis-files to MMC, then i would suggest you to get the firmware updated to 5.27.0 in nokia service. We'll see if there's some soft that cannot install under that, but i haven't yet used any.