RStudio initialization error, unexpected exception, fatal error

I am having an issue starting RStudio (desktop) that I did not have before.

When I fire-up RStudio, within seconds, the grey screen freezes with the following error message:

RStudio Initialization Error Unable to establish connection with R session

Once I click 'OK', I get the following two error messages:

RStudio Unexpected exception: The complexity of the regular expression exceeded predefined bounds...

and...

R encountered a fatal error. The session was terminated.

Any help in resolving these errors is much appreciated.

The "unexpected exception" error reads as though something's going wrong with RStudio trying to run something it's loading automatically as it is starting up. So, the related question is: how can I start RStudio fresh without opening any of the previous files/code/data?

I have tried uninstalling and reinstalling both R and RStudio, and R is installed fine (I can open and work on the R console).

I am working with:

Thank you!