Tryong to export things - "RFC communications error"

Hello,

I'm running through the [New Blog Series: ABAP Trial Version for Newbies|http://www.sdn.sap.com/irj/scn/weblogs?blog=/pub/wlg/6098] [original link is broken]; and i have a problem in [Part 8 ' Exporting development objects from SP8 '|http://www.sdn.sap.com/irj/scn/weblogs?blog=/pub/wlg/6360] [original link is broken];.

When I try to "Distribute and Activate Configuration" i got the error

RFC communications error with system/destination TMSADM_AT_NSP.DOMAIN_NSP     
Message no. XT101

Diagnosis
An RFC error occurred in the TMS communications layer.

  Target system: NSP.DOMAIN_NSP(001)
  Function: TMS_PS_WRITE_PROFILE_TO_DISK
  RFC message: Error when opening an RFC connection

which doesn't give me a clue whats going on. Is it related to the DNS-Stuff during installation? Web DynPro doesn't work for me, too...

Thank you for your help,

Martin