dbConnect error - unable to find an inherited method for function "show", for signature "PostgreSQLConnection" about rpostgresql HOT 1 CLOSED

I have the same error in the different use case. I believe my case is more 
clear and easy to reproduce.
I want to log API calls performed on market's API interface. Then I want to 
check the last API call time on particular market.

1.
Create empty table base on structure (I prefer to create this way as it fully 
reflects the data I'm going to store in that table):
dbWriteTable(conn = con, name = c('some_schema,'api_call'), value = 
data.table(market = character(), action = character(), api_call = 
as.POSIXct(NA,origin='1970-01-01',tz='GMT')[-1]), append = FALSE, row.names = 
FALSE)
It is working fine.

2.
Then I query the last API call on market - still I need to handle case when 
api_call table is empty:
dbGetQuery(conn = con, sql = "select api_call from some_schema.api_call where 
market = 'market_name' order by api_call desc limit 1")
I've got:
Error in (function (classes, fdef, mtable)  : 
  unable to find an inherited method for function ‘dbGetQuery’ for signature ‘"PostgreSQLConnection", "missing"’


I think the source of the issue might be in as.POSIXct(NULL,...) which I can 
handle in R by as.POSIXct(NA,...)[-1] as shown above, but such workaround might 
not be implemented in DBI/RPostgreSQL.

The best fix I think is to store the timestamp as integer but then I need to 
decode it in each interface that uses api_call data. I prefer to store normal 
timestamp there instead of integer. Any other way?

Win7 x64, R 3.0.2, postgres 9.3, RPostgreSQL 0.4

Regards