Test your dependencies. You might think that you have them all, but the chances are good that you don't. It's a common problem. Here's a little cpan shell script to get you started. After you ckeck the dependencies, then try reinstalling
Win32API::CommPort.
#!perl
use strict;
use autodie;
use warnings;
use CPAN;
CPAN::Shell->install(qw(
Task::DualLived
IO::Pty
Test::Pod
Devel::Symdump
Pod::Coverage
Sub::Exporter
Data::OptList
Params::Util
Pod::Eventual
IO::String
Mixin::Linewise::Readers
Pod::Coverage::TrustPod
Test::Pod::Coverage
Parse::CPAN::Meta
AppConfig
Template::Config
Unicode::Japanese
YAML
YAML::Syck
YAML::XS
YAML::Tiny
Test::YAML::Valid
Test::CPAN::Meta
Email::Address
Config::Tiny
PPIx::Regexp
String::Format
Perl::Tidy
Pod::Wordlist
Pod::Spell
Class::Data::Inheritable
Devel::StackTrace
Exception::Class
Readonly
PPIx::Utilities::Statement
Test::Deep
B::Keywords
Perl::Critic
Perl::Critic::Utils
IPC::Run3
Probe:Perl
Test::Script
File::Find::Rule::Perl
List::MoreUtils
Task::Weaken
Class::Inspector
Hook::LexWrap
Test::SubCalls
Clone
Test::Tester
Test::NoWarnings
Test::Object
File::Remove
PPI
Text::Glob
Number::Compare
File::Find::Rule
Perl::MinimumVersion
Test::MinimumVersion
IPC::Run
Digest::SHA::PurePerl
Digest::SHA256
Test::Manifest
Crypt::Rijndael
Crypt::Blowfish
Crypt::Blowfish_PP
Crypt::CBC
Crypt::CAST5
Crypt::DES
Crypt::RIPEMD160
Tie::EncryptedHash
Class::Loader
Convert::ASCII::Armour
Data::Buffer
Digest::MD2
Math::Pari
Crypt::Random
Crypt::Primes
Digest::SHA1
Crypt::DES_EDE3
Crypt::DSA
Crypt::RSA
Convert::ASN1
Convert::PEM
GnuPG
File::HomeDir
Data::Buffer
File::Which
Crypt::OpenPGP
Module::Signature
Test::Signature
Term::ReadKey
Device::Port
Win32::Process));