fatal exception(0) any hints?

[gcramat]

Hello,
I' ve been struggling for some days, now, trying to upload my Olimex esp8266-dev with a running sample, to no avail.
I' ve chosen the at sample distributed with the SDK (1.1.2) : compile&link is OK, and so is uploading using both ESPTOOL and the windows espressif tool. But the module refuses to run filling the UART (at about 76880 bauds )w/ fatal exception(0).
epc1=0x40240644 .....
According to the disassembly listing the offending instrucrion is:
fffe61 l32r a6, 4024065c <user_uart_wait_tx_fifo_empty+0x3cc>
I' ve also tried previous sdk (1.1.0 and 1.0.1) to no avail.
What is strange is that some time ago I managed to compile, download & run the at application ( I think with SDK 1.0.0 ) but , after tampering with others samples ( e.g. blinky ) I was no more able to burn a running version of anly app.
Any hint on a possible cause of this fatal exception?
TIA
Giancarlo

[gcramat]

Well, I' ve got no replies on this issue, so I'm going to close it myself: no power issues , the problems disappeared as soon as I moved to another module (same make and model): looks that somehow something went wrong with my first module ( not the flash, though ..)
Now, months and 2 SDK versions after my app is runing smoothly ( most of the time ) with some occasional reboot due to exception(0) at an address not so far away from the original one. The all important difference is that this happens only occasionally.
My personal final consideration: ESP is too good to be true, but probably not yet stable enough ( and sure closed sorce is not going to help )

[eriksl]

Random "exceptions" are mostly due to bad power supply. The exp8266 is quite picky on that. It may draw short peaks of considerate power. If you power supply can't handle that, prepare for random crashes.