Mahmoud Al Zahar the top Hamas leader in the Gaza strip admitted that there is internal dispute between him and the head of the polit-bureau in Damascus, Khalid Machan.Which is exactly what I have been saying since this "unity" deal was announced. This so called "agreement" was always a sham meant to put out a face of a united front for the PA's September diplomatic push, with no intent of following through and actually creating a true unity government - which is nearly impossible given the differing positions of Fatah and Hamas, and Hamas' desire to stay in power in Gaza.
Al-Zahar hinted during his interview with the BBC of the possibility of pressure being implemented to delay forming the new Palestinian government.
Al-zahar added that Fatah officials have asked to postpone the formation of the new government, until after September to avoid obstacles in front of the negotiations and the French initiative.
(I couldn't find the interview on the BBC site.)