Different main effect in MANOVA and two-way MANOVA? Which one do I use?

I did a MANOVA in SPSS and there is a significant main effect of the IV on only one of my two DVs. Then I did a two way ANOVA to include one more IV, but otherwise use the same variables I've used in the MANOVA (just entered one additional variable). However, suddenly the same IV that had a sig. effect on only one of the DVs in the one-way MANOVA now (in the two-way MANOVA) has a sig. effect on BOTH DVs...so do I interpret this effect or the one from the one-way MANOVA?

(The interaction in the two-way MANOVA is not significant btw, but I think that doesn't matter for my question)

Thank you