To echo the above statments (I'm good at that), a wired connection is much more reliable. I used to have a wireless rig for my guitar, but I had too many dropouts and switched back to wired. Personally, I'm starting to build all my cables myself. A) it's cheaper (as far as I'm concerned), and B) quality control begins and ends with me.
Definitly invest in a good cable tester, it'll solve many headaches down the line. The Qbox is a good one, but I'm waiting to purchase a rat sniffer/sender (which probably won't help you much because it's geared more towards
XLR)
linky.
I'd say to nix the wireless and redundant cable and invest/build quality
1/4" cable. THe problem you're running into, as wayne hoskins said, is that most
instrument cables that musos use are
poor quality, coupled with the fact that they're abused night after night, and they become the weak link in that signal chain. I've rarely had failures after the DI (once or twice, but those were from bad snake channels), but have plenty of stories of musos' cables crapping out on them. Just watch it lending out cables, rarely do the lent ones come back.