If you have that many distinct alarms you should use a software package like Win911 http://www.specterinstruments.com/
It is a very flexible software if you have different numbers for different alarms and times, also you can send email alerts as well as voice or text messages.
One thing you may want to check is the touch screen configuration, some of them allow you to write from the touch screen on start up which means tbe register in the touch screen overwrite the PLC. Possibly the touch screen is restarting occasionally and writing bogus values. Usually you can...
What about using a Pin and Sleeve connector? This is the service they are designed for and they sell non metalic units upto 100Amps. Woodhead is one of many companies that sell them.
http://www.woodhead.com/data/current3539/pin20and20sleeveNEW.pdf
Not sure if you solved your problem, but Emerson sells a conditioning orifice plate that only requires 2 pipe diameters. I have used them for purge air flow and they work great.
http://www.emersonprocess.com/rosemount/products/flow/conditioning_orifice_technology.html
I have had good luck with a PCMCIA Serial converter with all the AB serial products. Another thought is we have changed laptops to Panasonic C51 Toughbooks they still have serial ports and are nice machines.
Is it the the same location for the 10th node if so you could have a wiring issue. I had a client who had the DH+ line too close to a 480V line and when active all the nodes where affected. Just a thought.
The problem with micrologix is you need to purchase an RTC module to use the status registers for time. You can use the timers to schedule time based events but with the RTC module you can schedule by the time of day. Also check the time base for the timers they can be 1 sec, .01 sec or .001...
Look at Elpro wireless I/O it is a spread spectrum wire in wire out I/O system Omnex also makes a unit that works well. They are combined units with mixed I/O usually with 4-20 mA inputs/outputs and digital input/outputs.
This is a PLC forum group, to state PLC's are antiquated is a ridiculous statement. PLC's are current and have a market that will be around for a long time. Full PC automation control will need to be as reliable and durable as PLC's before they replace them I don’t see that happening for quite...