First, the list of what @INC contains would be useful.

Second, your use lib line uses a directory that is relative to the current working directory. I highly recommend switching that to something with an absolute path, even if that absolute path is dynamic. For example, if you want relative to the script, you can use:

use FindBin;
use File::Spec;
use lib File::Spec->catdir($FindBin::Bin, qw(System common Bio Tools))
+;
# or ...
use lib File::Spec->catdir($FindBin::Bin, qw(System common));
[download]

or something like that.

I would look to ensure that Bio::Tools::pICalculator is not only in that directory as perceived by the other nodes in the cluster, but is also readable by that user on all nodes. Note that if you're running as root, and using NFS to mount a common directory, it often gets clobbered to become an unprivileged user for permission purposes - so make sure the files are readable by all.

Update: added another use lib option based on suaveant's excellent observation.