Try entering this example script.
Compile it in LSL first. It compiles for me. Check that only the second state_entry, touch_start, and on_rez fire.
Now try compiling it in Mono. It just gives me an error, "Unable to upload" .. "due to the following reason: Assemble to CIL failed. Please try again later."

I ran into this because I added to a script of mine to test something, and it failed to compile in Mono. Oops, I had added a duplicate on_rez event.

Example script:

default
{
    touch_start(integer num_detected)
    {
        llSay(0,"First touch.");
    }
    state_entry()
    {
        llSay(0,"First state_entry.");
    }
    touch_start(integer num_detected)
    {
        llSay(0,"Second touch.");
    }
    state_entry()
    {
        llSay(0, "Second state_entry.");
    }
    on_rez(integer start_params)
    {
        llSay(0,"First on_rez");
    }
    on_rez(integer start_params)
    {
        llSay(0,"Second on_rez");
    }
}