NanoRoute doesn't route multi height design

Hello,

 as a test case I have a mixed design with 4 rows only. 3 standard core cell rows and 1 second row, that has a multiple of standard cell row height & pitch. Site definition is done properly. The design contains 2 cells only, one per each row. I created the floorplan, defined the globalNetConnect rules, routed the power. Placement and trialroute work fine. Everything is on grid.

Tech LEF is done properly

trialRoute:

Phase 1l Overflow: 0.00% H + 0.00% V (0:00:00.0 420.7M)

Congestion distribution:
Remain    cntH        cntV
--------------------------------------
--------------------------------------
  1:    0     0.00%    3     0.27%
  2:    0     0.00%    3     0.27%
  3:    0     0.00%    6     0.53%
  4:    98     8.73%    4     0.36%
  5:    1024    91.27%    1106    98.57%

 When I start NanoRoute I got this last line and it hangs up ... for hours maybe days.

 #NanoRoute Version v11.12-s011 NR121003-1304/11_10_USR2-UB
#Start routing data preparation.

 So I quit and try it again, The funny thing, I can route the nets manully without violations. If one cell is deleted before, NanoRoute routes. And further, I make a block of the multi height design, it can be routed properly. But  both type of cells together in one design doesn't work.

Has anyone  an idea, did I forgot something in the setup?

 Thanks & regards,

scudex