sh-3.1# whoami
root
sh-3.1# firefox
Bus error

I think I have plenty of memory to begin with:

sh-3.1# free
total used free shared buffers cached
Mem: 2076084 462256 1613828 0 96152 217408
-/+ buffers/cache: 148696 1927388
Swap: 0 0 0

sh-3.1# dmesg | tail
cloop: zlib decompression error -5 uncompressing block 16388 65536/65536/28802/0 399353147-399381949
Buffer I/O error on device cloop0, logical block 524436
cloop: zlib decompression error -5 uncompressing block 16388 65536/65536/28802/0 399353147-399381949
Buffer I/O error on device cloop0, logical block 524435
cloop: zlib decompression error -5 uncompressing block 16388 65536/65536/28802/0 399353147-399381949
Buffer I/O error on device cloop0, logical block 524436
cloop: zlib decompression error -5 uncompressing block 16388 65536/65536/28802/0 399353147-399381949
Buffer I/O error on device cloop0, logical block 524435
cloop: zlib decompression error -5 uncompressing block 16388 65536/65536/28802/0 399353147-399381949
Buffer I/O error on device cloop0, logical block 524436

why is this happening?

I did run the cheatsheet "knoppix testcd" and everything appeared to be OK.
.
C