Cryptic Errors. Probably a quick fix? ( noob )

Question

Completely confused. Tried to run latex script from yesterday on a different computer. Doesn't work now. here are my errors:

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.118     }
           ]pdfTeX warning (ext4): destination with the same identifier (name{e
quation.1.3}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.125     }
           pdfTeX warning (ext4): destination with the same identifier (name{eq
uation.1.1}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.125     }
           pdfTeX warning (ext4): destination with the same identifier (name{eq
uation.1.2}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.125     }
           pdfTeX warning (ext4): destination with the same identifier (name{eq
uation.1.4}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.144     }
           pdfTeX warning (ext4): destination with the same identifier (name{eq
uation.1.1}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.144     }
           pdfTeX warning (ext4): destination with the same identifier (name{eq
uation.1.2}) has been already used, duplicate ignored
<to be read again> 
                   \relax 
l.144     }

Overfull \hbox (8.95819pt too wide) in paragraph at lines 157--158
[]\OT1/lmr/m/n/10.95 Signal de-cay dis-tur-bances are char-ac-ter-ized by the p
er-tur-ba-tion of the nom-i-nal wave-form sig-nal, $\OML/lmm/m/it/10.95 v[]\OT1
/lmr/m/n/10.95 (\OML/lmm/m/it/10.95 t\OT1/lmr/m/n/10.95 )$,
[3pdfTeX warning (ext4): destination with the same identifier (name{equation.1.
2}) has been already used, duplicate ignored

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.159 ..._{perturbed}(t) = v_{nominal}(1 + d(t))$$
                                                  pdfTeX warning (ext4): destin
ation with the same identifier (name{equation.1.1}) has been already used, dupl
icate ignored

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.159 ..._{perturbed}(t) = v_{nominal}(1 + d(t))$$
                                                  pdfTeX warning (ext4): destin
ation with the same identifier (name{equation.1.2}) has been already used, dupl
icate ignored

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.159 ..._{perturbed}(t) = v_{nominal}(1 + d(t))$$
                                                  pdfTeX warning (ext4): destin
ation with the same identifier (name{equation.1.3}) has been already used, dupl
icate ignored

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.159 ..._{perturbed}(t) = v_{nominal}(1 + d(t))$$
                                                  pdfTeX warning (ext4): destin
ation with the same identifier (name{equation.1.4}) has been already used, dupl
icate ignored

\AtBegShi@Output ...ipout \box \AtBeginShipoutBox 
                                                  \fi \fi 
l.159 ..._{perturbed}(t) = v_{nominal}(1 + d(t))$$
                                                  ]

! LaTeX Error: Illegal character in array arg.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.171 ...\begin{tabular}{ | m | m | m | m{5cm} | }

? 
Process interrupted by user

Any ideas? Here is the code at line 118.

 \equations{
        d(t) &=    \lbrace \hat x \ast h \rbrace(t) \\
             &=    \lbrace x + n \ast h \rbrace(t) \\
             &=    \lbrace x \ast h \rbrace(t) + \lbrace n \ast h \rbrace (t)\\
             &:=    d_x(t) + d_n(t).\\
    }

where equations is a macro for:

\newcommand{\equations}[1]{ \begin{subequations} 
                                \begin{align}                                 
                                    #1 
                                \end{align}
                            \end{subequations} }

For reference, here are the included packages

\documentclass[11pt,a4paper]{article}
\usepackage[margin=1.5cm]{geometry}
\usepackage[english]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{marvosym}
\usepackage{multicol}
\usepackage{listings}
\usepackage{graphicx}
\usepackage{multirow}
\usepackage{hyperref}
\usepackage{lmodern}    % font definition
\usepackage{amsmath}    % math fonts
\usepackage{amsfonts}
\usepackage{slashed}
\usepackage{amsthm}
\usepackage{tikz}
\usepackage{tabu}           % tables, http://en.wikibooks.org/wiki/LaTeX/Tables

Windows 7, x32 texWorks version. Also, I have used latex "successfully" a number of times ( to the point of finishing the project ) but I have almost willfully avoided learning latex; for short term success, it seemed quicker to hack latex than actually learn it. But now that I'm actually trying to learn it, I feel stupid and lost and confused, and I'm going slower than when trying to hack it. It's quite possible due to my incompetency that I'm lacking some details.

Also, what typeset settings should I be using? LaTeX isn't even an option for some reason.

Thanks in advance.