http://s16.postimg.org/utxuwpo39/Capture.png
In flashing mode my connections are :
RXD --> TXD
GPIO0 --> RST
GPIO2 --> VCC
GND --> GND
VCC --> VCC (+3.3V)
RST --> left unconnected
CH_PD --> VCC
TXD --> RXD
While in normal operation mode my connections are :
RXD --> TXD
GPIO0 --> VCC
GPIO2 --> VCC
GND --> GND
VCC --> VCC (+3.3V)
RST --> left unconnected
CH_PD --> VCC
TXD --> RXD
maybe it's the RST pin that stayed unconnected ??