[R-sig-ME] Avoid errors in pwrssUpdate ?

[Pierre Morel]

Dear List,

I am getting a lot of pwrssUpdate errors when trying to model my data with gmler (using the most recent version from svn... I don't know if the previous versions were affected).

These errors are "PIRLS step failed" or "pwrssUpdate did not converge in 30 iterations". I understand that these means that the algorithm does not manage to work with my data, but there is a peculiar behavior, and my data doesn't seem too unreasonable to fit with the model I want to use, so I am wondering if the problem is on my side !

Here is a link toward a plot of part of my data as I want to model it (using ggplot2) : https://dl.dropbox.com/u/1205127/Images/glmer_plot.pdf
Each panel is for a subject of a behavioral experiment, and what is represented is the probability of the subject following a rule as a function of the weight given to this rule in the instructions (RuleWeight, between 0 and 1 here). Each point corresponds to a probability computed over 6 trials (points are jittered to see better).

Here is the model I want to fit, which doesn't seem unreasonable given the figure (random slopes and intercepts for subjects) :

model<-glmer(cbind(RuleReach,NTrials-RuleReach)~RuleWeight+(RuleWeight|Subject),data=rewardalldirsub,family=binomial)

However this gives me the "pwrssUpdate did not converge in 30 iterations" error. 
What is surprinsing, is that if I do not use the rightmost points (RuleWeight of 1), the model converges, even though there are less datapoints and the remaining points are the noisiest (subjects follow the rule quite reliably when it has a weight of 1 as you can see).

Removing the correlation in the random effects works sometimes (but not on all my sub data sets), and having a random intercept only (which is obviously not correct) is the only thing that seems to work in all cases.

Centering RuleWeight (ie having it between -1 and 1 instead of 0 and 1) doesn't work.

Any ideas on why this doesn't work / how to make it work ?

Thanks

Pierre Morel