beamer: Top-aligning columns within a top-aligned frame

Update

This known bug was solved some time ago. There is no need for workaround solutions or including special lines of code in preambles.

\documentclass{beamer}
\begin{document}
\begin{frame}[t]{Test Columns}
\begin{columns}
\column{.5\linewidth}
First Column
\begin{itemize}
\item First Item First Item First Item First Item
\item Second Item Second Item Second Item Second Item
\end{itemize}
\column{.5\linewidth}
Second Column
\begin{itemize}
\item First Item First Item First Item First Item
\item Second Item Second Item Second Item Second Item
\end{itemize}
\end{columns}
\end{frame}
\begin{frame}{Test Columns}
\begin{columns}
\column{.5\linewidth}
First Column
\begin{itemize}
\item First Item First Item First Item First Item
\item Second Item Second Item Second Item Second Item
\end{itemize}
\column{.5\linewidth}
Second Column
\begin{itemize}
\item First Item First Item First Item First Item
\item Second Item Second Item Second Item Second Item
\end{itemize}
\end{columns}
\end{frame}
\end{document}

works as expected

Original answer

This problem was reported (issue #78) at Github beamer development repository. The suggested solution was:

I know how to fix it, and it's quite easy, but I'm not sure if it will break something else. If you need the fix badly, replace lines 256--260 in beamerbaseframe.sty which read:

\def\beamer@initfirstlineunskip{%
  \def\beamer@firstlineitemizeunskip{%
    \vskip-\partopsep\vskip-\topsep\vskip-\parskip%
    \global\let\beamer@firstlineitemizeunskip=\relax}%
  \everypar{\global\let\beamer@firstlineitemizeunskip=\relax}}

with

\def\beamer@initfirstlineunskip{}%

Its state is still 'on hold'.

Instead of modifying beamer files, we can include some lines in our preamble.

\documentclass{beamer}
\makeatletter
\define@key{beamerframe}{t}[true]{% top
  \beamer@frametopskip=.2cm plus .5\paperheight\relax%
  \beamer@framebottomskip=0pt plus 1fill\relax%
  \beamer@frametopskipautobreak=\beamer@frametopskip\relax%
  \beamer@framebottomskipautobreak=\beamer@framebottomskip\relax%
  \def\beamer@initfirstlineunskip{}%
}
\makeatother   
\begin{document}    
\begin{frame}[t]{Frame title}
  \begin{columns}[t]
    \begin{column}{0.5\textwidth}
      \begin{itemize}
      \item First column, first item
      \item First column, second item
      \end{itemize}
    \end{column}
    \begin{column}{0.5\textwidth}
      \begin{itemize}
      \item Second column, first item
      \end{itemize}
    \end{column}
  \end{columns}
\end{frame}
\end{document}

You could set \topsep and \partopsep to zero. Here's a definition of an itemize version with this in mind, achieving vertical top alignment. It's similar to a solution I remember which Uwe Lück posted some time ago to a mailing list.

\documentclass{beamer}
\makeatletter
\newenvironment{myitemize}{%
   \setlength{\topsep}{0pt}
   \setlength{\partopsep}{0pt}
   \renewcommand*{\@listi}{\leftmargin\leftmargini \parsep\z@ \topsep\z@ \itemsep\z@}
   \let\@listI\@listi
   \itemize
}{\enditemize}
\makeatother   
\begin{document}    
\begin{frame}[t]{Frame title}
  \begin{columns}[t]
    \begin{column}{0.5\textwidth}
      \begin{myitemize}
      \item First column, first item
      \item First column, second item
      \end{myitemize}
    \end{column}
    \begin{column}{0.5\textwidth}
      \begin{myitemize}
      \item Second column, first item
      \end{myitemize}
    \end{column}
  \end{columns}
\end{frame}
\end{document}

It may be worth trying minipage, instead of creating the custom modifications in the preamble, especially if it is going to be something that is not used a lot of times:

\documentclass{beamer}

\begin{document}

\begin{frame}[t]{Frame title}
    \begin{minipage}[t]{0.45\textwidth}
        \vspace{0pt}
        \begin{itemize}
            \item First column, first item
            \item First column, second item
        \end{itemize}
    \end{minipage}%
    \hfill
    \begin{minipage}[t]{0.45\textwidth}
        \vspace{0pt}
        \begin{itemize}
            \item Second column, first item
        \end{itemize}
    \end{minipage}
\end{frame}

\end{document}

where the \vspace{0pt} is there just to give LaTeX a common reference to align the contents in both minipage.