NewBee - unknown "possible" memory leak?

Right, I guess it's unlikely to be Serial1 then. Can you try changing:

function onInit(){
var ow = new OneWire(A1);
var sensor = require("DS18B20").connect(ow);
sensor.setRes(12); 
digitalWrite([LED1,LED2,LED3],0b100);
var lcd = require("HD44780").connectI2C(I2C1);
I2C1.setup({scl:B8,sda:B9});
lcd.clear(); 
setTimeout("digitalWrite([LED1,LED2,LED3],0b010);", 1000);
setTimeout("digitalWrite([LED1,LED2,LED3],0b001);", 2000);
setTimeout("digitalWrite([LED1,LED2,LED3],0);", 3000);
// Delay start-up for diagnostics (above) and for LCD clear
I2C1.setup({scl:B8, sda:B9});
var rtc = require("DS3231").connect(I2C1);
}

to:

var ow,sensor,lcd,rtc;
function onInit(){
ow = new OneWire(A1);
sensor = require("DS18B20").connect(ow);
sensor.setRes(12); 
digitalWrite([LED1,LED2,LED3],0b100);
lcd = require("HD44780").connectI2C(I2C1);
I2C1.setup({scl:B8,sda:B9});
lcd.clear(); 
setTimeout("digitalWrite([LED1,LED2,LED3],0b010);", 1000);
setTimeout("digitalWrite([LED1,LED2,LED3],0b001);", 2000);
setTimeout("digitalWrite([LED1,LED2,LED3],0);", 3000);
// Delay start-up for diagnostics (above) and for LCD clear
I2C1.setup({scl:B8, sda:B9});
rtc = require("DS3231").connect(I2C1);
}

and removing the code you have below that also sets those sensors up? When you write var in a function, it defines a local variable - so you were defining those variables and then they were being forgotten when the function exited. That shouldn't have caused a memory leak, but it might have caused some problems.

Can you also try typing trace() right after you load the program (and copy/paste it to a file) and then 'trace()' after it's lost some memory (and save that to a file as well)? We can then just 'diff' the two traces and see if it's actually a bigger than normal string or similar that is causing the leak.