[R] commands overwritten

[Yuval Sapir]

Hi,
I am often re-use commands in R by using the arrows to retype them and modify for the new needs. This way, I don't need to write commands again, and I can modify the command by inserting/deleting/re-writing the command. Today, suddenly, re-writing change the commands as the "insert" function does in Word. for example - if I am standing in the middle of
>model<-glm(seeds~RIL+height); summary(model)
trying to re-write it to
>model<-glm(seeds~(RIL+height)^2); summary(model)
I get instead
>model<-glm(seeds~(IL+height)^2)ummary(model)

How can I get rid of this awkwardiness? (YES, I tried already to hit "insert" key....)
Thanks,
Yuval