Syntax checking sometimes stalls

What I describe below is not as-yet a huge problem for me so this is only a precautionary report.

In a v large, v complex fixed format F90/F95 program with a lot of cross referencing by the IDE from one source file to another, as I am currently working on, using SF 1.30, I am sometimes finding the syntax checker picking on one source file and getting in a huge strop about it. 

It throws a red error message at nearly every line (possibly even every line) of source code, and I don't just mean lines that might contain errors.  Even 'C' comment lines, which aren't source code at all, throw red error messages at me.

Knowing this can't be right, I check that all source files are saved, check that they are all added to the project, then click 'build project'.  Usually, compiles and builds fully without error.  Then when I click back open the source file tab that upset the IDE, I find it is STILL extremely cross with me, and the dozens of red error lines are all still there.  I wait ages, and they don't go away.

I have always managed to get rid of the problem, usually by closing everything, exiting SF, re-starting and re-loading, but I 'think' I have sometimes found (I can't remember this for sure), that the error messages don't always go away when I do this.

Sometimes, after this has been happening for 5 minutes or so and I've been trying to fix it, SF has crashed, and on re-starting it, I've found it fully cured.

I suspect (but again am far from sure) that this behaviour might be triggered by using F10 to switch syntax checking off and on again.

There is every possibility that what I describe is the result of something that I've done and not a problem with SF, but I report it just anyone else has experienced this sometimes and would care to follow it up with more information for Jeff.
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J.