Error opening a model in GID

[ritamgc]

Hello,
I have modeled a frame building in GID +OpenSees (which I have saved in my computer). However, when I'm trying to open the model, the following errors appears:
WARNING: Unknown field 'kNm^2'
WARNING: Error reading 'C:/Users/Rita/Desktop/Tentativa2': Error found in materials file Line=2455. 58 materials read

Can someone tell me what am I doing wrong? and how can I overcome this error?
I'm using the latest version for OpenSees problemtype (2.6.0).

Thanks in advance,
Rita