I don't think the hotfix is a problem because I can use it without any problem.
You must make sure 2 things
(1) License. The following license is working fine with me. Be sure that there is no other cadence license before this one. I had a cadence license for ic51 before this one and ic61 license got impacted. I got error message like you have. http://bbs.eetop.cn/viewthread.php?tid=321723&highlight=ic615
(2) The current patch is only working for 32bit. You must set CDS_AUTO_64BIT=NONE. I don't know why, after I installed ic615, this parameter is automatically set to "ALL" if you don't set it to "NONE". Use "setenv" to check this parameter.