If you have problems in Linux, or simply wish to have XSI working properly do the following.
Here is a little trick:
Download this file ( This is for 64bit ONLY!! ) click here (http://aipixels.com/temp/libX11.so.6_64BIT.tar.gz)
Download this file ( This is for 32bit ONLY!! ) click here (http://aipixels.com/temp/libX11.so.6_32BIT.tar.gz)
Unpack it and copy it to