if anyone's been dealing with the dreaded "line of death" when making large or intricate designs,

Am using older Mac G450 with a NEC usb card & the PCUT630 USB & FlexiCut8 Starter
start cutting a simple sign, 4 lines of text. Cuts one word, cuts second word, cuts two letters and as starts cutting "O" cuts straight down the vinyl "line of death" had to hit emergency stop.
Before I started this cut, I test cut one word, then test cut another word, I have already set the Production Manager to Packet size to 1000 and medium curve quality. & have pen in second slot & rechecked all graphics, plus the double pre-test,
Apparently the GLITCH is Not restricted to large or intricate designs.
What is really confusing & frustrating is that many folks are just cutting along with no problems, while some of us have to deal with "these" problems. It has to be some detail in the equipment/software set-up. I have this G450 set up exclusively for cutting, just the basic OSX 4.11 install and FlexiStarter, I transfer files for cut by Zip disk. the Pcut is connected by USB cable (high quality) to the USB2 on the Mac. I added several USB drivers, including Keyspan, but nothing else. I must presume that it is a Flexi issue, OR just TOO technical of a USB issue for me to grasp.
If anyone from SAI or USCutter could shed light on this issue, I for one would be seriously grateful.
