When using a CUE sheet generated by EAC in CDRWin, it tells, that the CUE sheet is not valid. When I have a look at the CUE sheet myself, I see that there are sometimes dozens of indecies that all have the same position. What can I do?

Try a different gap detection mode and if none removed that problem, you would have to edit these CUE sheets manually, removing all indecies bigger then 01 and indecies that have impossible possitions.