>>> I have the same error now with the latest beta (2011-02-05) if there's a folder defined in OSFONTDIR that doesn't exist.
>>> Is there a particular reason why the isdir(path) check in globpattern from l-dir.lua was removed?
>>> If I add it back then there's no error.
>>
>>The check broke other globbing (e.g. wildcard) and is not robust so I
>>removed it; I need more info about why/where it fails at your end.

Sure,

For example, I'm using:
export OSFONTDIR="/usr/local/share/texmf/fonts;$HOME/.fonts" (which was by accident,
because originally I was using /usr/local/share/fonts which exists),
where I have fonts in $HOME/.fonts, but my /usr/local/share/texmf/fonts does not exist.
"ls: cannot access /usr/local/share/texmf/fonts: No such file or directory"

Running mkiv beta gives me this error when I want to use a font that's located in $HOME/.fonts:
fontnames       > identifying system font files with suffix otf
fontnames       > adding path from OSFONTDIR: /usr/local/share/texmf/fonts
fontnames       > adding path from OSFONTDIR: /home/reviczky/.fonts
fontnames       > globbing path /usr/local/share/texmf/fonts/**.otf
! LuaTeX error /usr/share/texmf/tex/context/base/l-dir.lua:68: cannot open /usr/local/share/texmf/fonts/: No such file or directory
stack traceback:
        [C]: in function 'walkdir'
        /usr/share/texmf/tex/context/base/l-dir.lua:68: in function 'globpattern'
        /usr/share/texmf/tex/context/base/l-dir.lua:170: in function 'glob'
        /usr/share/texmf/tex/context/base/font-syn.lua:354: in function 'walk_tree'
        /usr/share/texmf/tex/context/base/font-syn.lua:766: in function 'method'
        /usr/share/texmf/tex/context/base/font-syn.lua:729: in function 'traverse'
        /usr/share/texmf/tex/context/base/font-syn.lua:765: in function 'analyzefiles'
        /usr/share/texmf/tex/context/base/font-syn.lua:829: in function 'identify'
        /usr/share/texmf/tex/context/base/font-syn.lua:854: in function 'load'
        /usr/share/texmf/tex/context/base/font-syn.lua:865: in function 'load'
        /usr/share/texmf/tex/context/base/font-syn.lua:1018: in function 'resolvedspecification'
        /usr/share/texmf/tex/context/base/font-syn.lua:1028: in function 'resolve'
        /usr/share/texmf/tex/context/base/font-def.lua:264: in function 'r'
        /usr/share/texmf/tex/context/base/font-def.lua:297: in function 'resolve'
        /usr/share/texmf/tex/context/base/font-def.lua:636: in function 'read'
        /usr/share/texmf/tex/context/base/font-ctx.lua:564: in function 'stage_two'
        <main ctx instance>:1: in main chunk.

Log attached.
Do you need anything else?

Adam