Inconsistency problem while building a code

I am trying to build a model with ccts Compiler. The Top model consists of reference models. When i tried first time with the model placed on the desktop, i had an issue with the make file. I tried to move my model to D: folder and issue was not resolved.But then i had a different issue with tlc_new.mex32 file. It compiled the first ref model w/o any issues but the second ref model encountered an out of memory issue while executing tlc_new.mex32 file. I tried once again by restarting the PC and it worked and the code was ready (therefore the file tree is correct and all make files and tlc files are correct too).

The other morning, i wished to generate the code once again and it said there were no compilers. I had a restart of my PC and the compilers were reappearing.

My question here is why there is an inconsistent behavior with code generation? Is there anything i should lookout every time?