[thefro526]

To the OP, I've found that Inventor 2011 seems to work best on 64-Bit systems with 4+ GB of Memory and 2.6GHz Processor +. Both my Work and Home Computers run 2011 on 64-Bit Windows 7 with 6GB of Memory and have 2.67 and a 2.9x GHz processor respectively.

When we did a Training Class at my Job there were a handful of 32 Bit computers that were a bit underpowered (2GB of Ram, 2GHz Processor) and they would crash as Inventor did some of the more complicated feature calculations.

It seems that it is possible for some of the sketch geometry and constraints to become so complicated that your Computer cannot solve them correctly which leads to crashing. I'd Suggest looking into upgrading your computer if possible.