Primstar/Blender/iMac

Hi Everyone, I'm really new to all this.  I've played with Blender on my laptop which runs Windows but now I'm trying to get it to work for serious on my new iMac.  I have to create some sculpties for the work I'm doing in Second Life.  However, I keep running into problems with setting it up.  I'm not a programmer so please be patient with me :-)  I can get the Import/Export to show the Second Life options and I can get the Build menu to come up when I request Add> Mesh> Sculpt Mesh.  When I get the Build menu, even if I change nothing in it, the screen flashes as if Blender is trying to create something and then it just freezes and I have to shut it down and reopen it.  I've tried all sorts of things to get past this point and I'm at my wits end!

Below are any details I think you might need in order to help me.  Please I'm getting desparate here!

  Model Name:    iMac  Model Identifier:    iMac11,1  Processor Name:    Intel Core i5  Processor Speed:    2.66 GHz  Number Of Processors:    1  Total Number Of Cores:    4  L2 Cache (per core):    256 KB  L3 Cache:    8 MB  Memory:    4 GB  Processor Interconnect Speed:    4.8 GT/s  Boot ROM Version:    IM111.0034.B00  SMC Version (system):    1.54f33

I'm running Primstar 1.0.0 and Blender 249.2