The mention of PuTTY set me thinking.... and apologies if this is what the other post was already saying...
Perhaps you could, perhaps it would be worth trying...
Cut the Arduino out of the picture altogether for the moment. "Talk" to your serial device directly from a PC with PuTTY or similar... see if it will "behave" then. Maybe there's nothing wrong with your Arduino or program... but rather a fault in what you are connecting to?
Another thing to look at... are the bits in the data stream inverted? A "gotcha" which arises, and gives garbled output. If the output your program gets is consistent, or somewhat so, this could be what's going on.
For more on PuTTY....
(There are also notes about other serial comms issues there.)
Hope something above helps.