I figured that this was a topic that was discussed before, though I couldn't find it. It turns out I was right 
Anyway, I tend to agree that the RAW say nothing to prevent a lance from getting 1-1/2 Strength bonus when used mounted. As a DM with an eye toward possible house rules, I also think that I like it better getting 1-1/2 Strength, because that is a decent representation of the tremendous force of a moving mount behind the lance. So in this case I like the RAW, even if it was from an unintentional ambiguity (which we will never know).
Thanks!

Anyway, I tend to agree that the RAW say nothing to prevent a lance from getting 1-1/2 Strength bonus when used mounted. As a DM with an eye toward possible house rules, I also think that I like it better getting 1-1/2 Strength, because that is a decent representation of the tremendous force of a moving mount behind the lance. So in this case I like the RAW, even if it was from an unintentional ambiguity (which we will never know).
Thanks!