Footnoting a footnote can be performed by placing a \footnotemark within a footnote, followed later by the accompanying \footnotetext. However, only a single footnote can be placed within a footnote because of footnote counter desynchronization. This problem was solved, but the solution turned out to be incompatible with the \hyperref package (despite disabling hyperfootnotes in the \usepackage{hyperref} declaration).
The below MWE demonstrates this incompatibility.
\documentclass[10pt]{article}
% comment the below line to resolve the footnote numbering problem
\usepackage[colorlinks=true,urlcolor=red,hyperfootnotes=false]{hyperref}
% solution proposed by Werner (begin)
\usepackage{letltxmacro}
\newcounter{fnmarkcntr}\newcounter{fntextcntr}
\makeatletter
\renewcommand{\footnotemark}{%
\@ifnextchar[\@xfootnotemark
{\stepcounter{fnmarkcntr}%
\refstepcounter{footnote}\label{footnotemark\thefnmarkcntr}%
\protected@xdef\@thefnmark{\thefootnote}%
\@footnotemark}}
\makeatother
\LetLtxMacro{\oldfootnotetext}{\footnotetext}
\renewcommand{\footnotetext}[1]{%
\stepcounter{fntextcntr}%
\oldfootnotetext[\ref{footnotemark\thefntextcntr}]{#1}
}
% solution proposed by Werner (end)
\begin{document}
This text has a footnote\footnote%
{Which contains a sub-footnote\footnotemark}
\footnotetext{This footnote should be labeled `2'}
\end{document}
Shown below is the output of the above code with the \usepackage{hyperref} command removed.

Shown below is the erroneous output of the above code with the \usepackage{hyperref} command included.

Note that inclusion of the hyperref package results in incorrect numbering of the nested footnote (0 instead of 2) and placement of an undesired (albeit correctly numbered) footnotemark in the body of the text (it should be placed in the footnote). This undesired footnotemark has been erroneously hyperlinked.
hyperrefincompatibility, it seems appropriate that you move the respective MWE ("Edit 2") to this new question. – lockstep Dec 19 '11 at 00:06hyperref. – lockstep Dec 19 '11 at 00:22hyperrefpackage is omitted. For simplicity, I will remove that -- it does not add anything substantive to the example. – user001 Dec 19 '11 at 00:24