On every recordable DVD there's a data flag telling players what type of disc it is.
Bitsetting, or booktyping as it's also known, is changing this disc type info from DVD+R (or +RW) to DVD-ROM and this is done for compatibility reasons.
Basically it fools the player into thinking the disc is an original pressed DVD which has a higher degree of compatibility with more players.
Not all writers support bitsetting but if yours does then you should turn this on permanently.
In Nero, go to the Recorder Menu >>> Choose Recorder and if necessary click the Options button to make the options at the bottom visible.
Change the booktype setting to DVD-ROM then try burning your disc again.
This will only done to DVD+ media as the specification for DVD- media doesn't support bitsetting.