I don't really know what happen, but I did put in the 192 cipher size and it is working now .... they really need to provide better debugging or log for user to read... it is not windows man .... it is linux!
Am currently battling to configure Archos OpenVPN client on my A43 IT, with firmware 2.4.19 (and as yet have been unsuccessful).
However there IS a way to make the client generate a log file which can then be used to help in debugging. Add the following to the Extra Arguments field in the OpenVPN advanced settings
In my case, the internal 16GB storage is mounted as /mnt/storage, so my argument reads:
--log /mnt/storage/openvpn.log [or whatever filename you want to use as a log file]
Hope this could be of some help