Version:           KSpread:1.4.0b, Qt: 3.3.4 (using KDE KDE 3.4.2)
Installed from:    Mandrake RPMs
Compiler:          gcc version 3.3.1 (Mandrake Linux 9.2 3.3.1-2mdk) Configured with: ../configure --prefix=/usr --libdir=/usr/lib --with-slibdir=/lib --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking --enable-long-long --enable-__cxa_atexit --enable-languages=c,c++,ada,f77,objc,java,pascal --host=i586-mandrake-linux-gnu --with-system-zlib
Thread model: posix  --enable-threads=posix --disable-checking --enable-long-long --enable-__cxa_atexit --enable-languages=c,c++,ada,f77,objc,java,pascal --host=i586-mandrake-linux-gnu --with-system-zlib
OS:                Linux

I tried opening an .XLS file created in MS Excel. The file had multiple sheets. 

I could see the memory being used by the system shoot up immediately. 

I have 392M RAM and 256MB Swap. Before opening this file, there was no swapping, and RAM being used was close to 140M. 

It immediately ate up all my RAM, and then the SWAP space got fully used up. 

I was unable to do anything, and had to reboot.