Well, for anyone still frustrated by not being able to flash their Aquastream XT to the most current firmware...I have found a solution!!! So here goes...
First off, forget what Shoggy said. Please, no offense Shoggy..I know you get touchy when people attack your advice but in this case, it really just adds superfluous confusion to an already frustrating situation.
Step 1) Ensure you have a printer port (25 pin LPT) on your PC. NOT an aftermarket card with an LPT port. It MUST be a native (soldered on your motherboard) LPT port. Something about connections through the ternary PCI bus screws the flasher up.
Step 2) Make sure you're running Windows XP (x86). I've tried the flash from Vista x86, Vista x64, and XP x64. All had limited success but the flash was never entirely successful. Additionally, make sure your printer port is recognized as an "ECP Printer Port". Nothing fancy like "Qualcomm LPT", etc.
Step 3) Run the parallel port flash updater. Choose the flash file. BEFORE pressing the start flash button, disconnect the power cable from the pump. Leave the USB cable CONNECTED. Now reconnect the power and press the "start flash" button. You must press the "start flash" button while the light on the pump is still SOLID RED. You'll have about two seconds to do this after you reconnect the power, before the red light starts to flash again. Don't ask me why this is, it just works.
Additionally: I installed a fresh copy of XP x86, then installed .NET 2.0, and finally the LPT flasher software. I'd also recommend using a switching diode if you make your own cable (AC recommends 1N414
. This is because switching diodes react better to out-of-phase currents that are known to plague parralel circuits in PC's (like LPT ports).
GOOD LUCK!!