If you have 1 GB of memory, you would have to enable HIGH MEM support in kernel. I don't know if there are kernel packages with HIGH MEM support but I generally compile my own kernels so I don't know. When I installed slack first on my new machine...it too showed about 800 MB memory (although I had 1 GB) but after kernel compile with high mem support...the memory is accounted for correctly.
Kernel compile is easy as long as you are ready to do a bit of work and obviously it teaches you a lot when you do that. Can you give us more info on your hardware. This way it would be lot easier for us to help you compile your kernel.
I would not know about the crash...I might be related to some other package conflict or a problem with shared library. Open up a terminal and try opening the app from there...like this
This will spew any errors back in the terminal.