could not find function "is" error - several RStudio and R versions


Been battling this for the last 4 hours. The error appeared after I updates RStudio and R and then persisted across all combinations of the recent 2018-2019 versions of RStudio and R. The reproducible example below.
RSTudio version: Version 1.2.1522

R version 3.5.2 (2018-12-20) -- "Eggshell Igloo"
Copyright (C) 2018 The R Foundation for Statistical Computing
Platform: x86_64-w64-mingw32/x64 (64-bit)

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Microsoft R Open 3.5.2
The enhanced R distribution from Microsoft
Microsoft packages Copyright (C) 2018 Microsoft Corporation

Using the Intel MKL for parallel mathematical computing (using 8 cores).

Default CRAN mirror snapshot taken on 2019-02-01.

n <- 10
<simpleError in is(obj, "ore.frame"): could not find function "is">


I also have a new mouse wheel scrollign problem in the new rstudio but that's a story for another post.

Would appreciate any help! Thank you!

Anybody?? This is clearly an RStudio error. I have the free version presumably without tech support. Should I reinstall the OS? Run debug tracing? I removed all files from %appdata% and let rstudio reinitialize them again and the error persists.

Thing I find confusing about this is you seem to run a standard release of R from

R version 3.5.2 (2018-12-20) -- "Eggshell Igloo"

and then R Open from Microsoft on top of it.

Microsoft R Open 3.5.2

Is this normal?

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