expert advice about common letter with some issue

imran786 wrote:tier 1 entre through VENTURE Capital
Application Sended on 28th Nov 2013
bio metric don 19/12/2013
Receive common cirular letter but stated as follows on 25/01/2014
Dear xxx
Although we would normally decide your application within 8 weeks from the date it submitted, unfortunately this is not going to possible in your case.
This is because your application raises exceptionally complex issues and we require further times to consider you case thoroughly and reach a decision.
i am sorry for delay with your application and for inconvenience this caused , please be assured that we are doing all we can to make decision on you case as quickly as possible.
we expect to make a decision on your application by 31\03\2014 but we will write to you again if this is not going to possible.
your faithfully
temporary migration team.

common issue ,nothing to worry,they might need some more checks..


question:
1) no interview letter until now or any intimation letter about that.
2) raises exceptionally complex issue ,------------------what is mean by this any big issue or miner still confuse.
any one please help.
thanks