By default when you download SIS from within mobile using is browser, or send SIS using Bluetooth to your device, it is saved in Phone's internal memory. So there's no room for bigger files if phone's memory is low. Nokia PC Suite also uses phone's memory for install SIS from PC.
There are workarounds. You can first save the SIS to memory card using PC card reader, and then insert it into mobile device and install it by opening the SIS from file manager on the device.
They other workaround is to split your SIS in multiple small parts (20MB each should be good). Some SWF2Go customers have successfully used this approach.
You can hard code the install drive in the PKG file, so the SIS is always installed in E: (memory card).
You can also send me your SIS so I can test on our test devices and suggest you better solution. (Upload on your server or http://drop.io/ account and send link to email@example.com)
// chall3ng3r //