I agree! Been having this problem for more than 2 years. Some will run lickety-split, others will take an hour and error out. Talked to support on this more than a few times with no real resolution other than the blame being put upon our local systems somehow. It's so very frustrating. Sometimes I will run a VERY SIMPLE report with no filters, just a date range, wait 20 minutes, and then end up grabbing a subscribed report that I've already sent to myself and applying filters on the excel spreadsheet. Easy-peasy, right? The shortest distance from point A to point B ends up being the scenic route. (And in case you were wondering, the original report never did finish running.)
It could be an indication of something processing on your marketo instance. When something large is processing in the background, I see a lot of strange things happening.
I have the same issue. It seems like any time you run a report with any filters at all, it crashes. Im currently running a report for "clicks link on a web page in the last 30 days" and it continually errors out. Surely these systems should be more robust.