AE cs6 disk cach settings

hi community

i'm rocking AE version 11.0.1.12

my system is a 2x 2.4ghz quad core intel xeon mac with 16gb ram. i'm on lion 10.7.4

following my upgrade to CS6 I have installed a new 120gb SSD to work as a cache to make use of the global performance cache.

this was all last week, so I haven't yet done any serious testing to see if this is really working, but I'm posting because every time I start up AE i get this dialog:

i've messed around with the preferences options for disk cache but this seems to happen whatever amount of drive space I've allocated.

currently I have it set to 60gb - half the size of this drive - but ideally I'd like to use the whole dang thing.

here's a screenshot of my cache prefs:

i should point out that there is nothing else on this drive. its a 120gb OCZ vertex3 esata internal  SSD.

i came to the forum as I can't find anything in the ae help docs or online relating to optimum settings for a dedicated SSD cache drive, so i'm not sure what I'm doing wrong... but I'm pretty sure I shouldn't be getting an error like this.

your input, as always is appreciated

dan