upgrade to latest firmware TL-WA801ND_V1_120309 http://www.tp-link.com/mx/support/download/?model=TL-WA801ND&version=V1#tbl_j
just make sure you are Ver1 as you posted

Just before I proceed to the upgrade, I'm wondering does the security type (or even the channel number) might have an impact on what I'm experiencing...The reason I'm asking is that I set up my TL-WA801ND on a different network, where the security has been changed from WPA2-PSK to WPA-PSK and the channel number also has changed to 1 (from 6 which was before). Now it seems that my HTC One X can obtain an IP from the repeater quite easily. Why is this happening?:confused:

As you posted on a different network means a different brand of modem not al devices work with all

A little confused. since you need to set up repeater, the wireless security type & channel should be the same with original wireless network

you may refer to the following link to check the settings.

http://www.tp-link.com/en/article/?faqid=250

Timothy Karssiens you are not A little confused.you are right decalingo is confused.

Timothy! Sorry for the confusion. Of course when I'm on Repeater mode, the wireless security type and channel number should be the same as the main AP. ;) What I meant was that if I change the security type and the channel number of my main AP, do you think I might get different result?

Anyway, as danymarc suggested, I upgraded my TL-WA801ND firmware to the latest one however still it seems that the repeater does not pass the DHCP packets from the main AP to my mobile.

That being said, Android doesn't seem to be the only reason why this setup is not working properly; because I tried my TL-WA801ND with a different brand of AP (MODACOM) and in this case Android phone can easily obtain an IP from the repeater.

Shall I use wireless bridging, instead of repeater mode?

OK! Bridge with AP...
Now I can have two different SSID on different channels. As it seems, the security is now limited to WEP only; so I need to essentially change my main AP security protocol from WPA2 to WEP. I suppose I need to enable DHCP on my TP-Link AP but do I have to modify the address range as well according to the address range on main AP as well?
By the way, shall I assign IP addresses to the gateway and DNS on my TP-Link too?

When we're using the AP in the Universal Repeater mode:
1) Do we essentially need to put router's IP address in the gateway address setting of the repeater or shall we leave it as 0.0.0.0?
2) The starting and end IP addresses in my router have been set to 192.168.1.100 and 192.168.1.149. The default IP address of my AP is 192.168.1.254. Shall I change my AP IP address to 192.168.1.X (X ranging from 100-149)?