Will ECC memory fix my DVR recording errors?

Probably not. Recording errors are almost never caused by memory bit flips. ECC memory corrects single-bit errors in RAM, but those errors are extremely rare in normal operation. A DVR system is far more likely to lose footage due to a failing hard drive, corrupted filesystem, camera signal interference, software bugs, or overheating. Spend the money on a good hard drive and a UPS instead.