I updated slitaz cooking recently and found that the graphing scripts I ran under cron failed. These used rrdtool update comands, which turned out to be the problem.
Running "rrdtool info data.rrd" failed, producing the output:
ERROR: This RRD was created on another architecture
This error occurred even though data.rrd was created and updated on the sltaz machine before the rrdtool package update.

Eventually, after checking with an rrd data file created on another 64bit machine, I concluded that rrdtool package was buggy. I downloaded the rrdtool from the stable package list, removed the recently updated cooking version, and installed the stable version.

Now everything works fine as before the update.