I've done some experimenting and research on throwing a serial port 0x17C error, which happens to be error 380 in decimal.
For MSCOMM32, error 380 is "Invalid Property" which ties in with what some people are reporting.
The 380 error is thrown when an error is made in setting the baud rate, stop bits and parity settings, but not necessarily exclusively then ( but it's not clear where else that could occur ). Trying to use a non-existant serial port should throw a different error.
That infers that the Programming Editor is trying to set the serial port settings wrongly ( unlikely I'd have thought as they are hard-coded into the executable ), or that MSCOMM32 ( or something ) is rejecting those settings.
One possibility could be that MSCOMM32 is not being registered with the OS as an ActiveX Control properly, or it isn't being properly marked as 'licensed for run-time use', although that too should show up as a different error, but I've been unable to test this. A completely missing MSCOMM32 gives a different error to 380 in my experience.
None of this really explains why 4.0.x works and 4.1.5/4.1.6 doesn't.
I suspected it may be an XP+SP2 problem, as it works on my 98SE fine, but posts indicate problems with 98 too.
One difference between mine and other user's setups is that my MSCOMM32 came with an MS product with a developer licence, which most home users won't have.
That again doesn't explain why 4.0.x works and the latest don't, unless uninstalling removes the MSCOMM32 component and installing puts it back, and that process is happening differently in each case. Windows usually leaves no end of 'rubbish' lying about after an installation so this doesn't alwys happen, but due to my setups I'm not prepared to start experimenting for fear of stopping my own PC's from working.
Having a look at what Mscomm32.* files exist and where, with what creation dates and sizes under the different cirumstances ( 4.0.x, 4.1.5, both uninstalled ) may provide some further pointers to what's going askew.
No one seems to have indicated if this error is happening with physical or virtual ( USB, netowrked etc ) serial ports; that information would also help greatly.