I should have mentioned that there's a similar problem with  
refcommand=authoryear (my previous post concerned  
refcommand=authoryears).

Using Mk IV, the first citation is preceded with a new line. Mk II  
behaves appropriately. And all citations other than the first one are  
formatted correctly by Mk IV.

This is quite similar to the problem I reported with  
refcommand=authoryears. In both cases, only the first citation is  
wrong and the error in both cases involves a line break. Perhaps they  
have a related cause. Happy hunting!

mjg

Samples are attached.

This is LuaTeX, Version beta-0.46.0-2009112820
  \write18 enabled.
(bib-test-2.tex

ConTeXt  ver: 2009.12.01 17:09 MKIV  fmt: 2009.12.1  int: english/ 
english