I have a class which handles SPTs, and it's defined like this:

Define Class spt As Table Of Table.prg
	Add Object params As Collection
	cSql=""
	cKeyExp=""
...

This has worked for months, in a dozen instances, without a hitch. Now I'm having a form which calls one of these to check against the item table on SQL server, which also works OK for the first document. Once this document is saved, it gives an error on next document, when it checks for the next item.

 [If Empty(This.params.GetKey(cName))] <-- this is where it happens

Unknown member PARAMS.(nr 1925) in program Sptitemmaster.setparam
 at line nr 189

Sometimes it even gives me an "unknown member This".
This doesn't happen regularly - I've tried to reproduce and went for several documents without a hitch. But I've seen it quite a number of times. I've even rebuilt with recompile, and it vanished for a while, then came back this morning.

Did anyone have something like this?