I have an example for which lmer() crashes with the last update of lme4  (version 0.999902345-0 with R-2.15.1 on Windows 32 bits) but not with version 0.999375-42 (2011-10-02, R-2.14.2 on Windows 32 bits).

*** The lmer() model is : 

lmer(y~1+(1|Part)+(1|Operator)+(1|Part:Operator),data=dat)


*** And the dataset is : 

Operator   Part   y
1  2  0.34
1  3  -1.23
1  5  -2.46
2  1  -0.84
2  1  -1.57
2  2  -0.31
2  3  -0.18
3  1  -0.94
3  1  -0.81
3  2  0.77
3  2  0.4
3  3  -2.37
3  3  -2.78
3  4  1.29
3  5  -0.95
4  1  -1.58
4  2  -2.06
4  3  -3.11
4  3  -3.2
4  4  -0.1
4  4  -0.49
4  5  -2.02
4  5  -0.75
5  1  1.71
5  2  -0.85
5  2  -1.19
5  3  0.13
5  3  1.35
5  4  1.92
5  5  1.04
5  5  1.08


Maybe it is more easy to get this dataset from here: 

http://stats.stackexchange.com/questions/31023/why-does-lmer-fails-with-this-dataset
	[[alternative HTML version deleted]]

