Hi,
You can reset the program back to its default settings by clicking on 'help' then select the bottom item 'Reset Program settings to default' - see if it has any effect.
When you say you get poor quality on scenes that are in bright light which file are you playing ... one exported to DVD ... the edited footage in MEP15 .... or the original untouched captured footage ?

If its either of the first two then you may have applied some kind of effect or processing eg gamma settings or other corrections or filter which is affecting the output either as you play back or as you export to DVD. If it is the original untouched captured footage that displays this effect then something may have gone wrong with the capture from tape ... try pulling in a short segment from indoors and one from outdoors to see if you get the same quality problem. Also, on import from DV tape do you record to DV format or to mpeg format if you have selected mpeg then try the uncompressed Dv format by unchecking the mpeg box.

Another thing you could try is running some similar footage that you have previously edited and exported successfuly through MEP15 - if you now get problems I think it could be a PC/ operating system/driver issue. Assuming no hardware faults then rolling progressively further back may get you running but it is important to try and figure out what the differences are between rollbacks so that you can avoid the issue returning.

Quite a lot to try but hopefully I've given you some things to check-out that may help ... let me know how you get on.