I have had this issue before and still can't make sense of it. If I do nothing to my FP as entered into the FMC, everything works perfectly. But after everything is entered and I go to the DEP/ARR page and select a SID and a runway (or even just change the runway when there is no SID), shouldn't the V-Speeds be automatically deleted causing me to go back to the TAKEOFF page to re-enter them? The problem is they aren't. After entering any changes in the DEP/ARR page the V-Speeds are still shown in the TAKEOFF page and on the NAV display. This rears its ugly head when I start my takeoff roll and engage the autothrottle (yes, I have armed the autothrottle prior to entering the active). At that time the V-Speeds get deleted (a check in TAKEOFF page of the FMC confirms that there are "---" in place of the V-Speeds). Then I am toast and have to end my flight because I can't get the autothrottle to engage in any mode. I have removed and re-installed all PMDG aircraft to see if someting was corrupted. But that has no effect.

Yes they should. Are the V speeds in large font or small font? If you are using FMC V speeds then you need to "harden them up" by selecting the keys immediately adjacent to each speed. If you are using tabulated speeds from a manual you will need to type each speed and line select it to the appropriate position. This will change the font to a larger style. If you selct a different runway or sid then the speeds will delete and you will get a message Take off speeds deleted.CheersSteve

Dan,Steve is 100% correct. It is normal for the FMC to delete the V-Speeds is you add/change the departing runway. V-Speed deletion is the FMC's way of saying "Hey, something has changed and you need to confirm the change".